Kubota U20-3 Workshop Manual
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Kubota U20-3 Workshop Manual

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Table of Contents

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WORKSHOP MANUAL
KUBOTA EXCAVATOR
U20-3
Code No.97899-60740

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Summary of Contents for Kubota U20-3

  • Page 1 WORKSHOP MANUAL KUBOTA EXCAVATOR U20-3 U25-3 Code No.97899-60740...

  • Page 3: Electrical System

    CONTENTS I General II Machine body ................. II Mechanism Section -M-1 • ................II Service Section -S-1 • III Engine ................III 05-M Series Engine • ................ III Mechanism Section -M-1 • ................III Service Section -S-1 • IV Hydraulic System ................

  • Page 5: Table Of Contents

    U20-3, U25-3 WSM General I. General A. Body and engine identification marks....................I-2 B. Safety precautions for servicing, disassembly and reassembly..........I-3 a. Safety measures before starting work ................I-3 b. Safety measures during work ................... I-3 c. Preparation for disassembly ..................... I-4 d.

  • Page 7: A. Body And Engine Identification Marks

    U20-3, U25-3 WSM General A.Body and engine identification marks (2)Engine serial number If trouble should occur during use, or if servicing is necessary, contact the dealer who handles the machine. At that time please inform the machine model and engine type and serial numbers.

  • Page 8: B. Safety Precautions For Servicing, Disassembly And Reassembly

    U20-3, U25-3 WSM General B.Safety precautions for servicing, disassembly and reassembly Safety precautions for servicing Most accidents during servicing arise from carelessness. Please remember that Safety involves both the welfare of the employees and improved work efficiency. Safety precautions for Disassembly and reassembly Machines must be disassembled and assembled efficiently and safely.

  • Page 9: C. Preparation For Disassembly

    U20-3, U25-3 WSM General c. Preparation for disassembly (1) Cleaning Remove mud and dirt from the body before disassembly. (2) Acceptance inspection The machine must be checked before it is disassembled to record existing conditions, such as those listed below.

  • Page 10: C. Important Safety Process And Critical Functional Process

    U20-3, U25-3 WSM General C.IMPORTANT SAFETY PROCESS AND CRITICAL FUNCTIONAL PROCESS The following instructions are related to essential adhesives, important safety process and critical functional process .Pay special attention in servicing these process. (Pay also close attention in reconnecting the electrical cables.) a.

  • Page 11: E. Servicing Fundamentals

    U20-3, U25-3 WSM General E.SERVICING FUNDAMENTALS a. Items for Servicing Locking adhesive (1) Tighten bolts, nuts, adapters,and similar parts to their specified torques which are given in the list of tightening torques and adhesive as well as in this manual. Be sure to observe the specified torques for important tightened parts and components.
  • Page 12 U20-3, U25-3 WSM General (4) Precautions in tightening hoses and pipes. • Flexible hoses have a slight natural bend of their own. Utilize the natural bend. Be also careful not to twist them. • Be careful not to confuse the routes of the hoses.

  • Page 13: B. O-Ring, Oil Seal, Circlip And Roll Pin

    U20-3, U25-3 WSM General b. O-ring, Oil seal, Circlip and Roll (1) General precautions • Make sure the O-ring and the oil seal are free of anything unusual (uneven surface, scratches, chipping, etc.). • Check the O-ring groove for burrs. Correct, if any, using an oil stone or the like.
  • Page 14 U20-3, U25-3 WSM General (4) Oil seal • Do not confuse the orientation of the oil seal lips. Direct the main lip toward the oil chamber; in other word, toward what is to be sealed. Packing Dustpans lip Metal ring...

  • Page 15: C. Piping

    U20-3, U25-3 WSM General c. Piping (1) General precautions • Tightening the pipe socket to the specified torque. If too tight, the socket itself or a hydraulic component may get damaged. It too loose, an oil leak may result. •...
  • Page 16 U20-3, U25-3 WSM General (4) Hose screw Metric Size Hose Torque Tightening torque Thread size N·m N·m Thread size (piping screw) Wrench size kgf·m kgf·m (piping screw) Union nut section Taper thread section 20 ~ 30 × 2.0 ~ 3.1 ·...
  • Page 17 U20-3, U25-3 WSM General (6) Tightening torque table for hose clamp (Screw type) Tightening torque Dia. (mm) Code No. N·m kgf·m Ø12 ~ 16 09318-89016 Ø19 ~ 25 09318-89024 2.5 ~ 3.4 25 ~ 35 Ø31 ~ 40 09318-89039 Ø36 ~ 46 09318-89045 Ø15 ~ 25...
  • Page 18 U20-3, U25-3 WSM General (8) Tightening torque of bolts and nuts Refer to the tightness torque table below. Bolts, Nuts Nominal Dia. SS41 S40C, S45C SCr4 7.8 ~ 9.3 N·m 9.8 ~ 11.3 N·m 12.3 ~ 14.2 N·m 0.80 ~ 0.95 kgf·m 1.00 ~ 1.15 kgf·m...
  • Page 19 U20-3, U25-3 WSM General (10)Washer-equipped elbow Tightening torque Size N·m kgf·m G1/4 25 ~ 30 2.5 ~ 3.0 G3/8 49 ~ 54 5.0 ~ 5.5 G1/2 59 ~ 64 6.0 ~ 6.5 G1/8 15 ~ 16.5 1.5 ~ 1.7 Tightening procedure 1.

  • Page 20: D. Machine Quality Specifications

    U20-3, U25-3 WSM General d. Machine Quality Specifications Machine specification:Service port, Wrist rest, STD-arm, KBT-cab, KBT-bucket Specifications Items Unit U20-3 U25-3 Remarks Main Spec. JIS A8404 Total length 3848 ± 77 4107 ± 82 (Transport) Total width 1400 ± 14 1500 ±...

  • Page 21: Table Of Contents

    U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks Max. digging radius 4136 ± 62 4501 ± 68 Ground level Max. 4023 ± 60 4386 ± 66 digging radius Ground level Min. Bucket bottom 1455 ± 44 1499 ± 30...
  • Page 22 U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks Engine performance Max. engine rpm no load 2400> 2600> 2 pump relief 2100< 2300< Dozer+2 pump relief 2100< 1800< Idling rpm 1250 ± 50 1350 ± 50 Travelling performance 300>...
  • Page 23 U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks 0.8 ± 0.3 1.0 ± 0.3 Ground to max. up Max. down to max. 2.6 ± 0.3 2.3 ± 0.3 Dozer speed down 1.0 ± 0.3 1.4 ± 0.3 Max. up to ground Max.
  • Page 24 U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks 220 ± 5 220 ± 5 kgf/cm 21.6 ± 0.5 21.6 ± 0.5 220 ± 5 220 ± 5 kgf/cm 21.6 ± 0.5 21.6 ± 0.5 Bench data Relief pressure setting 50 ±...
  • Page 25 U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks 1.34 ± 0.5 1.50 ± 0.5 crowd 13 ± 5 15 ± 5 Bucket lever 1.34 ± 0.5 1.50 ± 0.5 dump 13 ± 5 15 ± 5 1.34 ± 0.5 1.50 ±...
  • Page 26 U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks 1.2 ± 1 1.2 ± 1 12 ± 10 12 ± 10 Safety lock lever Up & down 3.5 ± 1.0 3.5 ± 1.0 down 34 ± 10 34 ± 10 1.5 ±...
  • Page 27 U20-3, U25-3 WSM General Specifications Items Unit U20-3 U25-3 Remarks >223 >293 Side >2189 >2877 Standard arm, static Bucket load to tip limited load fully >288 >372 Front >2833 >3654 Comfortability Canopy db(A) 80> 81> At operator's ear LPA db(A) 80>...

  • Page 28: F. Maintenance Intervals

    1000 h Filter Change air filter elements1.) 1000 h Change idler and track roller 2000 h Check altemator and starter Please contact your KUBOTA dealer. 2000 h motor Inspect electric cables and Please contact your KUBOTA dealer. annually connections every 2...

  • Page 29: B. Hydraulic Oil Check For Machines With Hydraulic Breakers

    U20-3, U25-3 WSM General b. Hydraulic Oil Check for machines with Hydraulic Breakers The Hydraulic oil change after 1000 operating hours in the operator’s manual is based on the type of work done. Following inspection measure are valid when hydraulic breakers are used: (1) Changing and filling up of hydraulic oil 1.

  • Page 30: C. Periodic Replacement Of Important Parts

    Hydraulic hose (Bucket cylinder) Hydraulic hose (Swing cylinder) Hydraulic hose (Dozer cylinder) Hydraulic hose (Service port) *2+2 Hydraulic hose (Swivel motor) Note: The *-marked hydraulic hoses are Kubota’s genuine ultra wear-resistant hoses. Be sure to use these parts. I-25...
  • Page 31 U20-3, U25-3 WSM Machine body (Mechanism section) II. Machine body (Mechanism section) A. Specifications ..........................II-M-2 a. Specifications .......................... II-M-2 b. Main dimensions ........................II-M-3 B. Components interchangeability ....................II-M-4 a. Bucket ............................II-M-4 C. Machine structure ........................II-M-5 a. Control linkage ........................II-M-5 b.
  • Page 33 U20-3, U25-3 WSM Machine body (Mechanism section) A.Specifications a. Specifications KUBOTA EXCAVATOR Model name U20-3 U25-3 Type canopy cabin canopy cabin Machine weight 2030 2120 2460 2540 Volume (CECE) 0.056 0.064 Standard bucket width (with side cutter) Type 3 cylinder...
  • Page 34 U20-3, U25-3 WSM Machine body (Mechanism section) b. Main dimensions U20-3 1400 1400 3970 2610 1780 2380 590 620 (760) 1300 (2320) 2320 1900 [280] 2920 930 3850 4030 4140 800 [1300/1500] [1300/1500] (3650) (1940) (2360) [330] CANOPY 4400 3020...
  • Page 35 U20-3, U25-3 WSM Machine body (Mechanism section) B.Components interchangeability a. Bucket Bucket can be mounted between current and new series in each local bucket as shown in the below table. Also below dimensions are for your reference to process local bucket in your place. Still bucket size and weight should be considered for safety, stability and performance.
  • Page 36 U20-3, U25-3 WSM Machine body (Mechanism section) C.Machine structure a. Control linkage [1] Traveling lever PART NAME Traveling lever, left Traveling lever, right Travel left section Travel right section Lock position Release position Traveling Lever Lock II-M-5...
  • Page 37 U20-3, U25-3 WSM Machine body (Mechanism section) [2] Dozer lever PART NAME Dozer lever Dozer cable Dozer section [3] Accelerator lever PART NAME Accelarator lever Accelarator cable II-M-6...
  • Page 38 U20-3, U25-3 WSM Machine body (Mechanism section) [4] Swing pedal PART NAME Swing Pedal Swing Section [5] Service port pedal PART NAME Service port Pedal Service port section II-M-7...
  • Page 39 U20-3, U25-3 WSM Machine body (Mechanism section) [6] Retractable track lever PART NAME Retractable track lever Retractable track cable Track section II-M-8...
  • Page 40 U20-3, U25-3 WSM Machine body (Mechanism section) b. Engine mount 10 9 PART NAME Bracket (1, Engine) Bracket (2, Engine) Bolt Rubber, cussionLock Bolt Washer, plain Washer, spring Bolt Spring, plate II-M-9...
  • Page 41 U20-3, U25-3 WSM Machine body (Mechanism section) PART NAME Unit, radiator Bracket, radiator Hose, inlet Tank, reserve Assy, airclearner Muffler Pipe, exast II-M-10...
  • Page 42 U20-3, U25-3 WSM Machine body (Mechanism section) c. Undercarriage [1] Tension spring PART NAME Assy. idler Assy. spring Bolt Assy. cylinder [2] Upper roller and Track roller PART NAME Assy. track roller Bolt Assy. upper roller Bolt Washer, spring II-M-11...
  • Page 43 U20-3, U25-3 WSM Machine body (Mechanism section) [3] Interchangeability between rubber and iron crawler • Fixed undercarriage U20-3 : required — : not required × PART No. PART NAME Q’ty Rubber crawler Steel crawler 06331-35012 Plug × — RB411-21812 Plate —...
  • Page 44 U20-3, U25-3 WSM Machine body (Mechanism section) • Retractable undercarriage (U20-3 only) U20-3 : required — : not required × PART No. PART NAME Q’ty Rubber crawler Steel crawler × 06331-35012 Plug — × RB411-21812 Plate — × 01133-61220 Bolt —...
  • Page 45 U20-3, U25-3 WSM Machine body (Mechanism section) [4] Retractable undercarriage Bring in slight contact without looseness. Lock the nut. Now make sure the extension blade lock pin can be smoothly pulled in and out. Bolt (10) (10) PART NAME Track frame, left...
  • Page 46 U20-3, U25-3 WSM Machine body (Mechanism section) [5] Rubber crawler Model U20-3 U25-3 Part No. RB411-22311 RB511-22311 Norminal size 250×47×84 300×53×80 Steel cord strength 5690 N/ Piece 9320 N/ Piece Steel cord number 15×2 21×2 Core steel pitch Core steel No.
  • Page 47 U20-3, U25-3 WSM Machine body (Mechanism section) [6] Steel crawler • U20-3 Link Bush II-M-16...
  • Page 48 U20-3, U25-3 WSM Machine body (Mechanism section) • U25-3 Hole shaft II-M-17...
  • Page 51 U20-3, U25-3 WSM Machine body (Service section) A.Specifications a. Machine weight STD. Arm unit U20-3 U25-3 Rubber crawler 2030 2460 Canopy Iron crawler Rubber crawler 2120 2540 Cabin Iron crawler II-S-2...
  • Page 52 U20-3, U25-3 WSM Machine body (Service section) b. Machine specifications STD. Arm Unit U20-3 U25-3 Engine Type Vertical, water-cooled 4 cycle, 4 cylinders diesel Model Kubota D1105-EBH-10 D1105-EBH-11 14.0/2200 15.5/2400 Output power (ISO9249) 19/2200 21/2400 Displacement 1123 Dimensions Overall length...
  • Page 53 U20-3, U25-3 WSM Machine body (Service section) c. Lever stroke and operating force Unit U20-3 U25-3 Remarks Stroke 72 / 72 72 / 72 Up / Down Boom 14 / 14 15 / 15 Force Up / Down 1.47 / 1.47 1.5 / 1.5...
  • Page 54 U20-3, U25-3 WSM Machine body (Service section) d. Dimensions of parts [1] Front pins Allowable wear Unit U20-3 U25-3 limit Pin diameter × length 40 × 164 40 × 164 Pin diameter × length 40 × 236 40 × 236 Pin diameter ×...
  • Page 55 U20-3, U25-3 WSM Machine body (Service section) [2] Bucket 1) Bucket dimensions Unit U20-3 U25-3 Remarks 76.3 × 9.5 76.3 × 9.5 563.5 563.5 78.5 78.5 145.7 145.7 14.5 14.5 NOTE: KUBOTA JAPAN BUCKET II-S-6...
  • Page 56 U20-3, U25-3 WSM Machine body (Service section) 2) Bucket installation relevant dimensions Unit U20-3 U25-3 Remarks 59.8 59.8 M12 × 1.25 M12 × 1.25 225.5 225.5 1015 1076.5 NOTE: KUBOTA JAPAN BUCKET STANDARD ARM II-S-7...
  • Page 57 U20-3, U25-3 WSM Machine body (Service section) [3] Rubber crawler Unit U20-3 U25-3 Remarks Crawler assy code No. RB411-2231-0 RB511-2231-0 Identification mark ∞ ∞ (Core steel rapping position) A : Lug height B : Link height C : Crawler width...
  • Page 58 U20-3, U25-3 WSM Machine body (Service section) [5] Track roller, idler, and sprocket Unit U20-3 U25-3 Remarks A : Guide width (A)/(B) 63 / 59 80 / 76 B : Outer diameter (A)/(B) 107 / 103 124 / 120 C : Roller width...
  • Page 59 U20-3, U25-3 WSM Machine body (Service section) [6] Dozer Unit U20-3 U25-3 Assy code No A : Pin diameter × length 40 × 125 40 × 125 B : Pin diameter × length 45 × 95 45 × 95 C : Pin diameter × length 45 ×...
  • Page 60 U20-3, U25-3 WSM Machine body (Service section) [7] Parts weight U20-3 U25-3 Remarks Track frame Swivel frame Swing bracket Boom Standard arm Long arm Bucket J.S.T.D Dozer Weight (left) Weight (right) Weight (rear) Rubber crawler Iron crawler Arch Engine Dry weight...
  • Page 61 U20-3, U25-3 WSM Machine body (Service section) [8] Water and oil quantity Unit U20-3 U25-3 Remarks Radiator Kubota LLC-N-50F Reserve tank Engine Crank case SAE10W30(CD) Hydraulic oil Full ISO 46 Hydraulic oil Tank 22.5 22.5 ISO 46 Wheel motor 0.33 0.33...
  • Page 62 U20-3, U25-3 WSM Machine body (Service section) B.Front attachment a. Parts designation II-S-13...
  • Page 63 U20-3, U25-3 WSM Machine body (Service section) (1) Swing bracket PART NAME PART NAME PART NAME Assy bracket, swing Bolt Bush Collar, Thrust Bush Pin, Joint Plate, Key Bush Pin, Sprit Bolt Bush washer, Plain Collar Nipple, Grease Bush Collar, Thrust...
  • Page 64 U20-3, U25-3 WSM Machine body (Service section) (5) Bracket Link PART NAME PART NAME PART NAME Seal, Dust Nipple, Grease Link, Bucket Nipple, Grease Bolt Link, Bucket Shim Washer Spacer Assy link, Bucket Nipple, Grease Washer, Plain Bush Shim Bolt...
  • Page 65 U20-3, U25-3 WSM Machine body (Service section) b. Exchange of bucket (Kubota Fitting the bucket 1.Place the O-ring on the boss of the bucket. Japan Bucket) 2.Align the arm with the hole A, put the shims at both ends of the arm, and couple them with CAUTION the pins.
  • Page 66 U20-3, U25-3 WSM Machine body (Service section) c. Exchange of bucket teeth and (2) Lock pin (4) Tooth adapter side cutters [JPN bucket version] 5. Align the holes of the point and adapter and knock in the rubber plug together with the lock...
  • Page 67 U20-3, U25-3 WSM Machine body (Service section) d. Installing of dust seal and thrust collar Installation of dust seal Install the dust seals in the direction as shown at left. If in the wrong direction, the sealing effect is adversely affected, which may get the pins worn out earlier.
  • Page 68 U20-3, U25-3 WSM Machine body (Service section) e. Installation of pin and bush [1] Pin bush 1) Front clearances (1) If the clearance at each support pin in the thrust direction is larger than 0.6 mm, add a shim. (2) Make sure the vertical clearance between the swivel frame and swing bracket is +0.3 mm to...
  • Page 69 U20-3, U25-3 WSM Machine body (Service section) [2] Pin, bush-(2) (16) (13) (14) (16) (15) (15) The *-marked parts are different between U20-3EU and U25-3EU. (18) Place the bucket links 2 and 3 with their machined faces inward. Place the bucket link 1 with its character-relief side inward (toward the machine).
  • Page 70 U20-3, U25-3 WSM Machine body (Service section) f. Front hose [1] Front hose assembly (U20-3) IMPORTANT: Replace the hydraulic hoses (boom, arm, bucket, swing, service port), after 2 years or 4000 operating hours, whichever comes earlier. [2] Front hose assembly (U25-3)
  • Page 71 U20-3, U25-3 WSM Machine body (Service section) [3] Hose clamp Hose guide Clamp (1, front) Hose Cord clamp Bucket hose route Bolt Pass the hoses below Cushion (rubber) the hose guide. Bolt Without SP Clamp (1, front) Plug Stay (harness clamp)
  • Page 72 U20-3, U25-3 WSM Machine body (Service section) C.Upper structure a. Lever and pedal 1) Assembling procedure 1. Adjust the levers neutral positions, setup [1] Travel lever directions and angles, referring to the figure at left. (1) Dimension between bracket front and...
  • Page 73 U20-3, U25-3 WSM Machine body (Service section) 2) Check items after setup Make sure the valve spool works all over the stroke. Make sure the valve spool moves smoothly. Lock the stopper bolt and nut tight enough. ever assembly (lock, travel)
  • Page 74 U20-3, U25-3 WSM Machine body (Service section) 3) Travel lever assembly view (3) Fitting the plastic cap (3) (11)(12)(13)(14)(15)(16)(17)(18)(19) Install the cap tight enough. (29)(30)(31) Otherwise the turning part may get (35)(36)(37) rusty. (4) Tightening torque of bolt (7) 60.8~70.6N m (6.2~7.2kgf...
  • Page 75 U20-3, U25-3 WSM Machine body (Service section) 4) Travel lever lock (1) Apply grease to the DU bushing bearing. (2) Tightening torque of adaptor G1/8:15.0~16.5N·m (1.5~1.7kgf·m) G1/4:24.5~29.4N·m (2.5~3.0kgf·m) (10) Part No. Part name Q’ty Remarks RG518-6611 Assy Cylinder (TL) 01123-60820...
  • Page 76 U20-3, U25-3 WSM Machine body (Service section) [2] Acceleration lever 1) Assembling procedure Acceleration lever assembly view (lever side) 1. Idling control 1250±50rpm 2. Set the engine rpm to maximum. Make sure the lever is exactly at the engine maximum rpm position.
  • Page 77 U20-3, U25-3 WSM Machine body (Service section) 2) Acceleration cable and hour meter cable routes * Minimum bending radius of cables: To be over 150R * Pass the cables along the shown routes without kink. 15272-67591 Cord clamp RB411-5329 Δ...
  • Page 78 U20-3, U25-3 WSM Machine body (Service section) 3) Acceleration cable and hour meter cable routes Step (5) RB411-5329A Cable (meter) RB411-3515 Δ Cable (acceleration) Muffler bracket 36200-77611 Cord clamp assembly 2 Pass between the swivel frame partition and frame (arch).
  • Page 79 U20-3, U25-3 WSM Machine body (Service section) [3] Dozer lever Dozer lever assembly view 1) Assembling Procedure 1. Adjust the levers neutral positions, referring to the figure at left. 2. Do not bend the end of the cable outer casing.
  • Page 80 U20-3, U25-3 WSM Machine body (Service section) [4] Swing and speed pedal Swing pedal assembly view 1. Apply grease to the DU bushing and makes sure the rotary shaft turns smoothly. 2. Tightening torque of link ball mock nut 39.2~45.1N m (4.0~4.6kgf...
  • Page 81 U20-3, U25-3 WSM Machine body (Service section) 4. Make sure the pedal swings equally right and left (horizontal at the center). To and fro →Service port Right and left →Swing 5. Fit the pedal with its top horizontal at the neutral position.
  • Page 82 U20-3, U25-3 WSM Machine body (Service section) [5] Limit switch 1) Assembling procedure Limit switch setup view 1. Tightening torque of limit switch 3.9~4.9N·m (0.4~0.5kgf·m) Apply screw LOCTITE. (Three- BondTB1401B) CAUTION Allow no gap at the points (A) and (B) when the limit switch is activated.
  • Page 83 U20-3, U25-3 WSM Machine body (Service section) b. Hydraulic oil tank Hydraulic oil tank assembling view 1) Assembling procedure 1. Installing the hydraulic oil tank assembly Tightening torque of bolt (15) 77.5~90.2N·m (7.9~9.2kgf·m) *Apply screw LOCTITE. (Loctite271) 2. Attaching the plug (13)
  • Page 84 U20-3, U25-3 WSM Machine body (Service section) c. Fuel tank and hose Fuel tank assembly view 1) Assembling procedure 1. Installing the sensor (fuel) Tightening torque of washer-fitted machine screw (6) : 3~4N·m (0.3~0.4kgf·m) 2. Tightness of fuel band Stretch allowance of fuel band out of the hydraulic oil tank: 23±1mm (reference)
  • Page 85 U20-3, U25-3 WSM Machine body (Service section) 2) Fuel hose MPORTANT: Replace the fuel hose after 2 years or 4000 operating hours, whichever comes earlier.I 3) Fuel hose routes II-S-36...
  • Page 86 Apply screw loctite.(Loctite 271) 2. Parts list Part No. Part name Q’ty Remarks Δ 1 RB419-4831 Counter weight (Cabin) U20-3 EU (Cabin type) Δ RB411-4831 in different color Blue No. 24 Δ RB519-4811 Counter weight U25-3 EU (Cabin,Cabin type) Δ...
  • Page 87 U20-3, U25-3 WSM Machine body (Service section) D.Cab canopy installation a. Installing the cabin or canopy [1] Installing the cabin (1)Nut Front, crosswise Back, crosswise Front in different color II-S-38...
  • Page 88 U20-3, U25-3 WSM Machine body (Service section) Tuck the front opening window in the ceiling to see if it can be tightly locked. [2] Canopy installation 1) Tightening torque of canopy lock screw (1)Bolt (2)Spring washer (3)Plain washer Front of the machine...
  • Page 89 U20-3, U25-3 WSM Machine body (Service section) [3] Heater setup Part No. Part name Q’ty Remarks RC418-42582 Pipe joint (R3/8-R1/2) (425) RC601-53541 Valve RB411-4181Δ Hose (1, WP heater) L=570 Adaptor/valve setup angle RB411-4182Δ Hose (2, WP heater) L=490 Hose clump (spring...
  • Page 90 U20-3, U25-3 WSM Machine body (Service section) Cord band Wire harness (heater conversion 2) Clamp the heater and harness. [4]Defroster setup Part No. Part name Q’ty Remarks RB419-4928Δ Hose (defroster, 700) RB419-4927Δ Hose (defroster, 400) RB419-4923Δ Cover (duct) 68768-4253Δ Grommet + 3...
  • Page 91 U20-3, U25-3 WSM Machine body (Service section) [5] Thermal insulation and sound Part No. Part name Q’ty Remarks absorber RB419-4591Δ Cover (left, cabin) Blue No.24 1. Before applying the thermal insulation and RB411-4591Δ in different color sound-absorbing sheet, check the surfaces 2 RB411-4117Δ...
  • Page 92 U20-3, U25-3 WSM Machine body (Service section) [6] Seat belt connection Europe-destined CAUTION: (1) Install the seat belt for both the cabin and canopy types. (2) Do not install the right-hand unload lever on both the cabin and canopy types.
  • Page 93 U20-3, U25-3 WSM Machine body (Service section) [7] Boom cylinder for cab type Cabin type Hydraulic cylinder, assembly (boom) Rad No.1 "M2C" marking in different color ) Bushing Bushing Cabin type Hydraulic cylinder, assembly (boom) Rad No.1 "M4C" marking Cylinder identification...
  • Page 94 U20-3, U25-3 WSM Machine body (Service section) E. Under carriage 1) Assembling procedure 1. Installing the bearing (swivel) a Swivel bearing Set the inner rings soft zone (marked “S”) Swivel bearing assembly view. at the left hand of the machine.
  • Page 95 U20-3, U25-3 WSM Machine body (Service section) c Track tension device 1) Assembling procedure 1. Make sure the unit slides smoothly in the track frame. 2. Tightening torque of idler assembly and tension spring plate: 77.5~90.2N·m(7.9~9.2kgf·m) Apply screw LOCTITE. (Loctite 547) 3.
  • Page 96 U20-3, U25-3 WSM Machine body (Service section) 3) Idler 1. Idler 2. Check the floating seal and the shafts O- ring for twist. 3. Apply lubricant to the floating seals sliding surface and the shafts O-ring. 4. The lube oil to pour is Engine Oil Class SAE#30CD.
  • Page 97 U20-3, U25-3 WSM Machine body (Service section) d Upper roller and track roller 1) Assembling procedure 1. Keep possible out-of-center between the ± sprocket, idler and track roller within (with the idler loosely fitted). CAUTION When jacking up the machine, place wooden blocks or the like under the lower frame to prevent the machine from falling.
  • Page 98 U20-3, U25-3 WSM Machine body (Service section) 4) Track roller disassembling procedure 1. Check the roller surface and shaft for wear, and measure the outside diameter, as required. If out of spec, replace them with new ones. 2. In reassembling, be careful to keep the roller inside and incoming parts free from dust, cuttings and other foreign matters.
  • Page 99 U20-3, U25-3 WSM Machine body (Service section) 5) Carrier roller disassembling procedure 1. Check the roller surface and shaft for wear, and measure the outside diameter, as required. If out of spec, replace them with new ones. 2. Put a bladed screwdriver at the cap side to disassemble the roller.
  • Page 100 U20-3, U25-3 WSM Machine body (Service section) 1. In reassembling, be careful to keep the roller inside and incoming parts free from dust, cuttings and other foreign matters. 2. The lube oil to pour is Engine Oil Class SAE#30CD. Its specified amount is 60cc.
  • Page 101 U20-3, U25-3 WSM Machine body (Service section) e. Crawler replacement and tension adjustment Move the rubber crawler until the joint Rubber crawler Seam joint marking (∞) comes at the top center Upper roller (see left) and the upper roller comes between the links.

  • Page 102: Width Mm

    U20-3, U25-3 WSM Machine body (Service section) f. Variable track (U20-3) [1] Dimensional view [2] Service data Items different from standard specifications only) New-model delivery guideline Reference Item Movement Unit Allowable range Remarks value Overall width (retracted) 1300 1287~1313 Overall width (extended)
  • Page 103 U20-3, U25-3 WSM Machine body (Service section) [3] Track frame Bolt (stopper) 4 pcs. Spring washer 4 pcs. Discontinued as from the 7th unit in August production Frame (track, center): discontinued as from Hirakata production lot Blade (right) Frame (Frack, right)
  • Page 104 U20-3, U25-3 WSM Machine body (Service section) [4] Blade Q’ty Interchange Dwg. No. Part No. Part name Remarks ability RB411-7460-0 Blade, assembly (center) Weight about 93 kg RB411-7455-0 Bushing (405030) RC411-7445-0 Collar 06616-25010 Grease nipple RC411-6678-0 Dust seal (405042) 50 in out. dia. 40 in inn. dia high DR type dust seal (φ40)
  • Page 105 U20-3, U25-3 WSM Machine body (Service section) [5] Track cylinder (17) Track frame Blade (19) (17) Bolt Dust seal (405042) Plan washer Bushing(405030) Spacer Collar (19) Pin(40-125) (18) Cylinder(blade)-Blade, track frame Pin (40-95) Bolt Plan washer (18) (18) (17) Cylinder identification...
  • Page 106 U20-3, U25-3 WSM Machine body (Service section) [6] Blade cylinder Hydraulic cylinder assembly(blade) "M2D"markings Bushing Dust seal Main specifications φ30A Rod outside diameter φ60A Tube inside diameter φ75A Tube outside diameter Stroke 215A 450A Maximum stretch Between the centers of pins at...
  • Page 107 U20-3, U25-3 WSM Machine body (Service section) [7] Hydraulic hose 1) List of high-pressure hoses (Upper route) Part No. Size Color of Location Part name Q’ty Hose configuration Remarks Fixed track (mm) tape Variable track reference Pump~C/VP3 Hydraulic hose RB411-6464Δ...
  • Page 108 U20-3, U25-3 WSM Machine body (Service section) 3) Hydraulic hose routes horizon Ensure a clearance with the track frame. 4) Travel wheel motor setup Part No. Part name Q’ty Remarks RB411-1443Δ Drive sprocket (111) 01128-61025 Bolt M10×1.5 9T Motor, assembly RB411-6129Δ...
  • Page 109 U20-3, U25-3 WSM Machine body (Service section) 5) Blade piping Q’ty Interchange Dwg. No. Part No. Part name Remarks ability RB411-7521-2 Cover (blade cylinder) 01133-61016 Bolt M10×16L×1.25p 7T 48.1~55.9N·m(4.9~5.7kgf·m) RB411-6376-0 Pipe joint(L, G 1/4 - G 1/4) 04810-00110 O-ring Class 1B (hard) P (fixing·movable) nominal dia11mm...
  • Page 110 U20-3, U25-3 WSM Machine body (Service section) 7) Left-travel piping Q’ty Interchange Dwg. No. Part No. Part name Remarks ability RB411-6394-0 Straight pipe joint (3-3-50) 04810-00140 O-ring Class 1B (hard) P (fixing·movable) nominal dia14mm 68728-7615-0 Adaptor 04810-00110 O-ring Class 1B (hard) P (fixing·movable) nominal dia11mm...
  • Page 111 U20-3, U25-3 WSM Machine body (Service section) [8] Control valve Maker: Kayaba Industry Model: KVSE-36-11 Weight: About 34 kg Q’ty Interchange Dwg. No. Part No. Part name Remarks ability RB411-6113-0 Control valve, assembly (variable) Variable track RB411-7012-0 Valve, assembly (width)
  • Page 112 U20-3, U25-3 WSM Machine body (Service section) [9] Swivel joint 1) Precautions in disassembling/reassembling (1) Tightening torque of hydraulic adaptor G1/4:24.5~29.4N·m(2.5~3.0kgf·m) G3/8:49.0~53.9N·m(5.0~5.5kgf·m) (2) Installing on the track frame Tightening torque: 166.7~196.1N·m(17.0~20.0kgf·m) Apply screw LOCTITE.(Loctite 271) (3) Before setting up, check the packings for scratches, deformation and other troubles.
  • Page 113 U20-3, U25-3 WSM Machine body (Service section) [10] Track stretch lever 1) Precautions in disassembling/reassembling (1) Do not bend the tip of the cable outer casing. Ensure the end straight at least 20 mm long. (2) Apply grease to the rotary bearing. Make sure it moves smoothly.
  • Page 114 U20-3, U25-3 WSM Machine body (Service section) [11] Counterweight 1) Precautions in disassembling / reassembling (1) Tightening torque of counterweight: 367.7~431.5N·m (37.5~44.0kgf·m) Apply screw LOCTITE. (Loctite 271) (2) Before applying the thermal insulation and sound-absorbing sheet, check the contact surfaces for oil and dust. Clean the surfaces as required.

  • Page 115: M Series Engine

    U20-3, U25-3 WSM Engine III. Engine A. 05-M Series Engine WSM ......................III-2 a. Engine Specifications for construction machinery ..............III-4 b. Dimensions ..........................III-8 III-1...
  • Page 117 This Workshop Manual has been prepared to provide servicing personnel with information on the mechanism, service and maintenance of KUBOTA Diesel Engine 03-M Series. It is divided into two parts, “Mechanism” and “Servicing” for each section. Mechanism Information on the Features and New Mechanisms are described.
  • Page 118 U20-3, U25-3 WSM Engine III-3...
  • Page 119 U20-3, U25-3 WSM Engine a. Engine Specifications for construction machinery U20-3EU U25-3EU Model D1105-EBH-10 D1105-EBH-11 No. of cylinder ← 78.0 × 78.4 ← Bore × Stroke 3.07 × 3.09 ← 1123 ← Displacement 68.53 ← kW/rpm 14.0/2200 15.5/2400 Max. output/rpm...
  • Page 120 U20-3, U25-3 WSM Engine Engine electric components U20-3EU U25-3EU D1105-EBH-10 D1105-EBH-11 ← Fuel injection pump type BoschMDtype mini-pump ← Nozzle type DN4PDN mini-nozzle ← 13.7-14.7 ← Injection pressure kgf/cm 140-150 ← 1991-2133 ← Dynomo 12V360W Manufacturer P/N 1G070-6401Δ ← Regulator adjusting voltage 12V14A ←...
  • Page 121 U20-3, U25-3 WSM Engine Performance curves Model D1105-EBH-10 III-6...
  • Page 122 U20-3, U25-3 WSM Engine Performance curves Model D1105-EBH-11 III-7...
  • Page 123 U20-3, U25-3 WSM Engine b. Dimensions III-8...
  • Page 125 U20-3, U25-3 WSM Engine (Mechanism section) III. Engine (Mechanism section) A. Feature ............................III-M-2 B. Engine body ..........................III-M-3 [1] Cylinder block ........................III-M-3 [2] Cylinder head ......................... III-M-3 [3] Crankshaft ..........................III-M-4 [4] Piston and piston rings ......................III-M-4 [5] Connecting rod ........................
  • Page 127 U20-3, U25-3 WSM Engine (Mechanism section) A.Feature III-M-2...
  • Page 128 U20-3, U25-3 WSM Engine (Mechanism section) B.Engine body [1] Cylinder block [2] Cylinder head III-M-3...
  • Page 129 U20-3, U25-3 WSM Engine (Mechanism section) [3] Crankshaft [4] Piston and piston rings III-M-4...
  • Page 130 U20-3, U25-3 WSM Engine (Mechanism section) [5] Connecting rod [6] Rocker arm [7] Camshaft III-M-5...
  • Page 131 U20-3, U25-3 WSM Engine (Mechanism section) [8] Fuel camshaft [9] Flywheel III-M-6...
  • Page 132 U20-3, U25-3 WSM Engine (Mechanism section) C.Lubricating system [1] General III-M-7...
  • Page 133 U20-3, U25-3 WSM Engine (Mechanism section) [2] Oil pump [3] Relief valve III-M-8...
  • Page 134 U20-3, U25-3 WSM Engine (Mechanism section) [4] Oil filter cartridge [5] Oil pressure switch III-M-9...
  • Page 135 U20-3, U25-3 WSM Engine (Mechanism section) D.Cooling system [1] General [2] Water pump III-M-10...
  • Page 136 U20-3, U25-3 WSM Engine (Mechanism section) [3] Thermostat [4] Radiator (not included in the basic engine) III-M-11...
  • Page 137 U20-3, U25-3 WSM Engine (Mechanism section) [5] Radiator cap III-M-12...
  • Page 138 U20-3, U25-3 WSM Engine (Mechanism section) E.Intake / exhaust system [1] Air cleaner (not included in the basic engine) [2] Muffler (not included in the basic engine) III-M-13...
  • Page 139 U20-3, U25-3 WSM Engine (Mechanism section) F. Fuel system [1] General [2] Injection pump III-M-14...
  • Page 140 U20-3, U25-3 WSM Engine (Mechanism section) III-M-15...
  • Page 141 U20-3, U25-3 WSM Engine (Mechanism section) III-M-16...
  • Page 142 U20-3, U25-3 WSM Engine (Mechanism section) [3] Injection nozzle [4] Fuel filter (not included in the basic model) III-M-17...
  • Page 143 U20-3, U25-3 WSM Engine (Mechanism section) [5] Governor III-M-18...
  • Page 144 U20-3, U25-3 WSM Engine (Mechanism section) III-M-19...
  • Page 145 U20-3, U25-3 WSM Engine (Mechanism section) [6] Automatic advance timer (not included in the basic model) III-M-20...
  • Page 146 U20-3, U25-3 WSM Engine (Mechanism section) III-M-21...
  • Page 147 U20-3, U25-3 WSM Engine (Mechanism section) G.Electrical system [1] Charging system III-M-22...
  • Page 148 U20-3, U25-3 WSM Engine (Mechanism section) H.Turbo charger system III-M-23...
  • Page 149 U20-3, U25-3 WSM Engine (Mechanism section) III-M-24...
  • Page 150 U20-3, U25-3 WSM Engine (Mechanism section) III-M-25...
  • Page 151 U20-3, U25-3 WSM Engine (Mechanism section) III-M-26...
  • Page 152 U20-3, U25-3 WSM Engine (Mechanism section) III-M-27...
  • Page 153 U20-3, U25-3 WSM Engine (Service section) III. Engine (Service section) A. Engine mount on the machine ....................III-S-3 B. General ............................III-S-10 [1] Engine identification ......................III-S-10 [2] General precaution .......................III-S-11 [3] Tightening torques .......................III-S-12 [4] Troubleshooting ........................III-S-13 [5] Servicing specifications .......................III-S-16 [6] Maintenance check list ......................III-S-25...
  • Page 154 U20-3, U25-3 WSM Engine (Service section) G. Electrical system ........................III-S-83 CHECKING ..........................III-S-83 [1] Starter .............................III-S-83 [2] Glow plug ..........................III-S-84 DISASSEMBLING AND ASSEMBLING ................III-S-84 [1] Starter .............................III-S-84 [2] Alternator ..........................III-S-85 SERVICING ..........................III-S-88 [1] Starter .............................III-S-88 [2] Alternator ..........................III-S-90 H. Turbo charger system ......................III-S-93 CHECKING ..........................III-S-93...
  • Page 155 U20-3, U25-3 WSM Engine (Service section) A.Engine mount on the machine (1) Engine bracket [1] Assembling procedure 1) Tightening torque of engine bracket: Engine bracket assembly view 48.1~55.9N⋅m (4.9~5.7kgf⋅m) * Apply screw loctite (Loctite 271). 2) Tightening torque of anti-vibration rubber: 77.5~90.2N⋅m (7.9~9.2kgf⋅m)
  • Page 156 U20-3, U25-3 WSM Engine (Service section) (2) Radiator [1] Detaching the radiator 1) Park the machine on a level floor. Bring down the front attachment and blade on the floor. 2) Remove the bonnet and the right side cover. 3) Remove the drain plug from the bottom of the radiator to let out all cooling water.
  • Page 157 U20-3, U25-3 WSM Engine (Service section) Radiator assembly view 1 [2] Reassembling the radiator 1) Clearance between radiator core (fin) and fan (part A): 60-67 mm * Keep the fan stretching evenly out of the fan shroud. 2) Clearance between fan and fan shroud (part...
  • Page 158 U20-3, U25-3 WSM Engine (Service section) Radiator assembly view 2 3) Parts list Part name Q’ty Remarks Radiator, assembly Shroud (fan) Sound absorber (shroud, 1) Sound absorber (shroud, 2) Sound absorber (shroud, 3) Bolt M6×1 Cover (fan) Cord clamp Bolt M6×1...
  • Page 159 U20-3, U25-3 WSM Engine (Service section) Radiator assembly view 3 a) Radiator Clamp to the inlet hose Suction hose, to be passed along center Catch the rubber’s hook tightly III-S-7...
  • Page 160 U20-3, U25-3 WSM Engine (Service section) (3) Muffler Muffler assembly view 1 [1] Reassembling procedure 1) Reassembling steps Temporarily tighten the bolts (A), (B) and (C). → Make sure there is no gap at the bolts. First tighten up the bolt (A).
  • Page 161 U20-3, U25-3 WSM Engine (Service section) (4) Fan belt Engine assembly view [1] Reassembling procedure 1) Tightening torque of fan flange bolt: 7.8~8.8N⋅m (0.8~0.9kgf⋅m) Fit the fan in position, referring to the figure at left. 2) Tightening torque of sensor (temperature): 62.7~72.5N⋅m (6.4~7.4kgf⋅m)
  • Page 162 U20-3, U25-3 WSM Engine (Service section) B.General [1] Engine identification III-S-10...
  • Page 163 U20-3, U25-3 WSM Engine (Service section) [2] General precaution III-S-11...
  • Page 164 U20-3, U25-3 WSM Engine (Service section) [3] Tightening torques III-S-12...
  • Page 165 U20-3, U25-3 WSM Engine (Service section) [4] Troubleshooting III-S-13...
  • Page 166 U20-3, U25-3 WSM Engine (Service section) III-S-14...
  • Page 167 U20-3, U25-3 WSM Engine (Service section) III-S-15...
  • Page 168 U20-3, U25-3 WSM Engine (Service section) [5] Servicing specifications III-S-16...
  • Page 169 U20-3, U25-3 WSM Engine (Service section) III-S-17...
  • Page 170 U20-3, U25-3 WSM Engine (Service section) III-S-18...
  • Page 171 U20-3, U25-3 WSM Engine (Service section) III-S-19...
  • Page 172 U20-3, U25-3 WSM Engine (Service section) III-S-20...
  • Page 173 U20-3, U25-3 WSM Engine (Service section) III-S-21...
  • Page 174 U20-3, U25-3 WSM Engine (Service section) III-S-22...
  • Page 175 U20-3, U25-3 WSM Engine (Service section) III-S-23...
  • Page 176 U20-3, U25-3 WSM Engine (Service section) III-S-24...
  • Page 177 U20-3, U25-3 WSM Engine (Service section) [6] Maintenance check list III-S-25...
  • Page 178 U20-3, U25-3 WSM Engine (Service section) [7] Check and maintenance III-S-26...
  • Page 179 U20-3, U25-3 WSM Engine (Service section) III-S-27...
  • Page 180 U20-3, U25-3 WSM Engine (Service section) III-S-28...
  • Page 181 U20-3, U25-3 WSM Engine (Service section) III-S-29...
  • Page 182 U20-3, U25-3 WSM Engine (Service section) III-S-30...
  • Page 183 U20-3, U25-3 WSM Engine (Service section) III-S-31...
  • Page 184 U20-3, U25-3 WSM Engine (Service section) III-S-32...
  • Page 185 U20-3, U25-3 WSM Engine (Service section) III-S-33...
  • Page 186 U20-3, U25-3 WSM Engine (Service section) III-S-34...
  • Page 187 U20-3, U25-3 WSM Engine (Service section) III-S-35...
  • Page 188 U20-3, U25-3 WSM Engine (Service section) III-S-36...
  • Page 189 U20-3, U25-3 WSM Engine (Service section) III-S-37...
  • Page 190 U20-3, U25-3 WSM Engine (Service section) III-S-38...
  • Page 191 U20-3, U25-3 WSM Engine (Service section) C.Engine body CHECKING AND ADJUSTING III-S-39...
  • Page 192 U20-3, U25-3 WSM Engine (Service section) DISASSEMBLING AND ASSEMBLING III-S-40...
  • Page 193 U20-3, U25-3 WSM Engine (Service section) [1] Draining water and oil [2] External components III-S-41...
  • Page 194 U20-3, U25-3 WSM Engine (Service section) [3] Cylinder head and valves III-S-42...
  • Page 195 U20-3, U25-3 WSM Engine (Service section) III-S-43...
  • Page 196 U20-3, U25-3 WSM Engine (Service section) [4] Gear case III-S-44...
  • Page 197 U20-3, U25-3 WSM Engine (Service section) III-S-45...
  • Page 198 U20-3, U25-3 WSM Engine (Service section) III-S-46...
  • Page 199 U20-3, U25-3 WSM Engine (Service section) III-S-47...
  • Page 200 U20-3, U25-3 WSM Engine (Service section) III-S-48...
  • Page 201 U20-3, U25-3 WSM Engine (Service section) III-S-49...
  • Page 202 U20-3, U25-3 WSM Engine (Service section) [5] Piston and connecting rod III-S-50...
  • Page 203 U20-3, U25-3 WSM Engine (Service section) III-S-51...
  • Page 204 U20-3, U25-3 WSM Engine (Service section) III-S-52...
  • Page 205 U20-3, U25-3 WSM Engine (Service section) [6] Flywheel and crankshaft III-S-53...
  • Page 206 U20-3, U25-3 WSM Engine (Service section) III-S-54...
  • Page 207 U20-3, U25-3 WSM Engine (Service section) SERVICING [1] Cylinder head III-S-55...
  • Page 208 U20-3, U25-3 WSM Engine (Service section) III-S-56...
  • Page 209 U20-3, U25-3 WSM Engine (Service section) III-S-57...
  • Page 210 U20-3, U25-3 WSM Engine (Service section) III-S-58...
  • Page 211 U20-3, U25-3 WSM Engine (Service section) III-S-59...
  • Page 212 U20-3, U25-3 WSM Engine (Service section) [2] Timing gear and camshaft III-S-60...
  • Page 213 U20-3, U25-3 WSM Engine (Service section) III-S-61...
  • Page 214 U20-3, U25-3 WSM Engine (Service section) [3] Piston and connecting rod III-S-62...
  • Page 215 U20-3, U25-3 WSM Engine (Service section) III-S-63...
  • Page 216 U20-3, U25-3 WSM Engine (Service section) III-S-64...
  • Page 217 U20-3, U25-3 WSM Engine (Service section) [4] Crankshaft III-S-65...
  • Page 218 U20-3, U25-3 WSM Engine (Service section) III-S-66...
  • Page 219 U20-3, U25-3 WSM Engine (Service section) III-S-67...
  • Page 220 U20-3, U25-3 WSM Engine (Service section) III-S-68...
  • Page 221 U20-3, U25-3 WSM Engine (Service section) III-S-69...
  • Page 222 U20-3, U25-3 WSM Engine (Service section) III-S-70...
  • Page 223 U20-3, U25-3 WSM Engine (Service section) [5] Cylinder III-S-71...
  • Page 224 U20-3, U25-3 WSM Engine (Service section) III-S-72...
  • Page 225 U20-3, U25-3 WSM Engine (Service section) D.Lubricating system CHECKING SERVICING [1] Oil pump III-S-73...
  • Page 226 U20-3, U25-3 WSM Engine (Service section) III-S-74...
  • Page 227 U20-3, U25-3 WSM Engine (Service section) E.Cooling system CHECKING [1] Fan belt [2] Radiator III-S-75...
  • Page 228 U20-3, U25-3 WSM Engine (Service section) DISASSEMBLING AND ASSEMBLING III-S-76...
  • Page 229 U20-3, U25-3 WSM Engine (Service section) III-S-77...
  • Page 230 U20-3, U25-3 WSM Engine (Service section) F. Fuel system CHECKING AND ADJUSTING [1] Injection pump III-S-78...
  • Page 231 U20-3, U25-3 WSM Engine (Service section) III-S-79...
  • Page 232 U20-3, U25-3 WSM Engine (Service section) [2] Injection nozzle III-S-80...
  • Page 233 U20-3, U25-3 WSM Engine (Service section) DISASSEMBLING AND ASSEMBLING [1] Injection pump III-S-81...
  • Page 234 U20-3, U25-3 WSM Engine (Service section) [2] Injection nozzle III-S-82...
  • Page 235 U20-3, U25-3 WSM Engine (Service section) G.Electrical system CHECKING [1] Starter III-S-83...
  • Page 236 U20-3, U25-3 WSM Engine (Service section) [2] Glow plug DISASSEMBLING AND ASSEMBLING [1] Starter III-S-84...
  • Page 237 U20-3, U25-3 WSM Engine (Service section) [2] Alternator III-S-85...
  • Page 238 U20-3, U25-3 WSM Engine (Service section) III-S-86...
  • Page 239 U20-3, U25-3 WSM Engine (Service section) III-S-87...
  • Page 240 U20-3, U25-3 WSM Engine (Service section) SERVICING [1] Starter III-S-88...
  • Page 241 U20-3, U25-3 WSM Engine (Service section) III-S-89...
  • Page 242 U20-3, U25-3 WSM Engine (Service section) [2] Alternator III-S-90...
  • Page 243 U20-3, U25-3 WSM Engine (Service section) III-S-91...
  • Page 244 U20-3, U25-3 WSM Engine (Service section) III-S-92...
  • Page 245 U20-3, U25-3 WSM Engine (Service section) H.Turbo charger system CHECKING III-S-93...
  • Page 246 U20-3, U25-3 WSM Engine (Service section) III-S-94...
  • Page 247 U20-3, U25-3 WSM Engine (Service section) DISASSEMBLING AND ASSEMBLING III-S-95...
  • Page 248 U20-3, U25-3 WSM Engine (Service section) III-S-96...
  • Page 249 Structure & specifications ....................IV-M-33 b. Operating principle ......................IV-M-34 c. Function of negative brake ....................IV-M-36 G. Rotary joint (Swivel joint) ......................IV-M-37 H. Travel motor U20-3 (Fujikoshi) ....................IV-M-39 a. Stracture & specifications ....................IV-M-39 b. Operating principle .......................IV-M-40 U25-3 (Kayaba) ........................IV-M-44 a. Structure & specifications ....................IV-M-44 b.
  • Page 251 U20-3, U25-3 WSM Hydraulic system (Mechanism section) A.Features of hydraulic system Function Detail Arm regeneration. Part of return oil from the arm cylinder rod is allowed to flow to the arm cylinder bottom, speeding up the arm's crowding and preventing the arm's getting stuck.
  • Page 252 U20-3, U25-3 WSM Hydraulic system (Mechanism section) B.Hydraulic system specifications Machine model U20-3 U25-3 Engine RPM 2,200 2,400 Pump Maker Fujikoshi Fujikoshi Type PVD-OB-24P-6G3-4694A PVD-OB-24P-8G3-4837B Variable Displacement Pump Variable Displacement Pump +Gear Pump +Gear Pump Delivery rate P1, P2 23.0 L / min 28.8 L / min...
  • Page 253 U20-3, U25-3 WSM Hydraulic system (Mechanism section) C.Main pump a. Structure & specifications PARTS NAME Q’ty PARTS NAME Q’ty PARTS NAME Q’ty PARTS NAME Q’ty Body S Rod G None Hex nut Body H None Plug Sealing washer Shaft None...
  • Page 254 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. Performance curve U20-3 Type: PVD-OB-24P-6G3-4649A 21.6 20.6 Operating Pressure kg / cm Displacement cc / rev 10.5 Discharge Capacity L / min 23.0 12.8 0.5 → 20.6 shift pressure 5 → 210...
  • Page 255 U20-3, U25-3 WSM Hydraulic system (Mechanism section) U25-3 Type: PVD-08-24P-8G3-4837B 21.6 17.2 Operating Pressure kg/cm Displacement cc/rev 12.0 Discharge Capacity 28.8 19.2 0.5 → 17.2 shift pressure 5 → 175 kg/cm Operating RPM 2,400 Rotating direction Weight U25-3 11.6cc/rev =195kgf/cm...
  • Page 256 U20-3, U25-3 WSM Hydraulic system (Mechanism section) c. Operating principle 1) Outline This compact, lightweight hydraulic pump has a Discharge groove P mechanism that provides for the performance of Suction groove (1) two variable pumps. Yet it needs as small a space Discharge groove P as for just one conventional pump.
  • Page 257 U20-3, U25-3 WSM Hydraulic system (Mechanism section) D.Control valve a. Specifications Machine model U20-3 U25-3 Type KVSE-36-10 KVSE-36-10 Section width 31.0 31.0 Total length 390.5 390.5 Main spool dia Spool stroke Pilot section Mechanical section Main relief valve setting pressure +0.3...
  • Page 259 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. General view of control valve U20-3: P/N RB411-61151 Return spring force Setup direction marker (TRAVEL, SERVICE, SWING, DOZER). grooves for the bucket, 4N at neutral, 108N at full stroke boom, arm and swivel spools...
  • Page 260 U20-3, U25-3 WSM Hydraulic system (Mechanism section) U25-3: P/N RB519-61151 Return spring force Setup direction marker (TRAVEL, SERVICE, SWING, DOZER). grooves for the bucket, 4N at neutral, 108N at full stroke boom, arm and swivel spools BACKWARD 21-PF 3/8 14 -PF1/4...
  • Page 261 U20-3, U25-3 WSM Hydraulic system (Mechanism section) c. Sectional view Bucket section PARTS NAME Q’ty Poppet for simultanious operation of boom & bucket HOUSING SPOOL SPRING SEAT SPRING SPRING SEAT O RING BOLT POPPET SPRING PLUG O RING POPPET Boom section PARTS NAME Q’ty...
  • Page 262 U20-3, U25-3 WSM Hydraulic system (Mechanism section) Travel (right) section PARTS NAME Q’ty HOUSING SPOOL O RING WIPER SEAL PLATE SPRING SEAT SPRING CAP SCREW BOLT BOLT POPPET SPRING PLUG Section C-C Inlet section PARTS NAME Q’ty HOUSING SPOOL O RING...
  • Page 263 U20-3, U25-3 WSM Hydraulic system (Mechanism section) Arm section PARTS NAME Q’ty Valve housing Spool Poppet Spring Plug O-ring Spring seat Spring Spring seat O-ring Socket head bolt Poppet Spring Plug Orifice plug Plug O-ring O-ring O-ring Section X-X IV-M-13...
  • Page 264 U20-3, U25-3 WSM Hydraulic system (Mechanism section) Service section PARTS NAME Q’ty HOUSING SPOOL O RING WIPER SEAL PLATE SPRING SHEET SPRING CAP SCREW BOLT BOLT POPPET SPRING PLUG O RING Swivel section PARTS NAME Q’ty HOUSING SPOOL SPRING SEAT...
  • Page 265 U20-3, U25-3 WSM Hydraulic system (Mechanism section) Dozer section PARTS NAME Q’ty HOUSING SPOOL O RING WIPER SEAL PLATE SPRING SEAT SPRING CAP SCREW BOLT BOLT POPPET SPRING PLUG O RING Travel straight section PARTS NAME Q’ty HOUSING SPOOL SPRING SEAT...
  • Page 266 U20-3, U25-3 WSM Hydraulic system (Mechanism section) d. Arm regeneration circuit (1) Arm dump Arm dump Pilot secondary pressure (2) Arm crowd Arm crowd Pilot secondary pressure • When oil flows through the hydraulic pilot passage shown at left above, the spool shifts rightward and the neutral passage gets closed.
  • Page 267 U20-3, U25-3 WSM Hydraulic system (Mechanism section) e. Boom anti-fall valve (1) At neutral position of boom section The hydraulic oil at port B (cylinder rod side) is shut off. The hydraulic oil at port A (cylinder bottom side) flows through the passage C and poppet "d" into the chamber Z.
  • Page 268 U20-3, U25-3 WSM Hydraulic system (Mechanism section) (2) Boom up (with port Pa under pressure) When the boom is lifted, the oil from the pilot valve is introduced into the port Pa and the control valve spool is moved to the lift.
  • Page 269 U20-3, U25-3 WSM Hydraulic system (Mechanism section) Details of the anti-drift valve operation Throttling effect Boom cylinder Poppet "d" Anti-drift poppet The oil from the pump comes pushing through the anti-drift poppet into the boom cylinder. The oil also passes through the poppet "d" and reaches behind the anti-drift poppet.
  • Page 270 U20-3, U25-3 WSM Hydraulic system (Mechanism section) (3) Boom down (with port Pb under pressure) When the boom is lowered, the oil from the pilot valve is introduced into the port Pb and the control valve spool is moved to the right. The hydraulic oil from the pump flows through parallel passage, pushing load check valve.
  • Page 271 U20-3, U25-3 WSM Hydraulic system (Mechanism section) Details of the anti-drift valve operation Pressure oil from pilot valve Piston No pressure oil flowing to Pi Pressure oil flowing to Pi Poppet "d" Chamber Z Part of the oil from the pilot valve is introduced into port Pi of the anti-drift valve, thereby pushing down the piston.
  • Page 272 U20-3, U25-3 WSM Hydraulic system (Mechanism section) f. Straight travel circuit (1) Feature The following points are ensured even when a front attachment (boom, arm, bucket, etc.) is operated while traveling. 1) The machine keeps running straight. 2) The machine keeps running at the same speed.
  • Page 273 U20-3, U25-3 WSM Hydraulic system (Mechanism section) equv. equv. equv. equv. equv. equv. equv. equv. equv. equv. equv. equv. 1. Set the travel lever to forward. (One of the oil flow from P4 is blocked at 2. Raise the boom, and another oil flow from pilot pump P4 gets blocked at the boom section.
  • Page 275 U20-3, U25-3 WSM Hydraulic system (Mechanism section) g. Simultaneous operation of boom & bucket While the boom and bucket are being used together, the pressure oil to the bucket switch is fed via the intermediate orifice. The orifice openness is not enough to cover the difference with respect to the attachment load, but designed to keep the best balance for simultaneous operation of the boom and bucket.
  • Page 276 U20-3, U25-3 WSM Hydraulic system (Mechanism section) h. Relief valve/Anti-cavitation valve Function of relief valve (1) The pressure oil passes first through the piston that is built in the main poppet. It then goes through the orifice B and fills the chamber A.
  • Page 277 U20-3, U25-3 WSM Hydraulic system (Mechanism section) i. Automatic air bleeding in hydraulic pilot section Automatic air bleeding mechanism is provided at the control valve spool which is operated by hydraulic pilot valve. (1) When the spool of the control valve is at neutral position.
  • Page 278 U20-3, U25-3 WSM Hydraulic system (Mechanism section) E.Pilot valve a. Structure The construction of pilot valve is shown in the sectional view (page 16). The casing has a vertical hole in which a reducing valve is integrated. The reducing valve consists of spool (201), secondary pressure setting spring (241), return spring (221), spring washer (216) and washer 2 (217).
  • Page 279 U20-3, U25-3 WSM Hydraulic system (Mechanism section) IV-M-28...
  • Page 280 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. Pilot valve control diagram IV-M-29...
  • Page 281 U20-3, U25-3 WSM Hydraulic system (Mechanism section) c. Function 1. Basic function The pilot valve is intended to control the stroke and direction of the control valve spool. To do this, the output pressure of the pilot valve is applied to the end of the control valve spool.
  • Page 282 U20-3, U25-3 WSM Hydraulic system (Mechanism section) 3. Operation The behavior of the pilot valve is discussed, referring to the hydraulic circuit diagram (Fig. 1) and behavior diagrams (Figs. 2, 3 and 4). Fig. 1 shows a typical application of the pilot valve.
  • Page 283 U20-3, U25-3 WSM Hydraulic system (Mechanism section) 2) With the lever being tilted (See Fig. 3.) When the lever is tilted and the push rod (212) gives a stroke, the spool (201) (spring seat (216)) lowers, which interconnects the port P and output ports (2 and 4).
  • Page 284 U20-3, U25-3 WSM Hydraulic system (Mechanism section) F. Swing motor a. Structure & specifications • Specification U20-3 U25-3 Type 25PB20A1124-C 25PB25A1125-C Displacement cc/rev 63.4 75.4 Theoretical RPM at 12.4 L / min at 18.4 L / min N·m 62.1 64.0 Theoretical output torque kgf·m...
  • Page 285 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. Operating principle 1. High-pressure oil coming via the main port 3. Now under hydraulic pressure, the rotor of the flows through the disc valve and valve plate rotor subassembly starts the planetary motion.
  • Page 286 U20-3, U25-3 WSM Hydraulic system (Mechanism section) When the high-pressure oil comes in the In other words, the rotors center makes 6/7 turn compartments 2, 3 and 4, as shown in Fig. 1, the around point A from B thorough B’ to B”. In Fig. 4, rotor in internal contact with the stator starts point B”...
  • Page 287 U20-3, U25-3 WSM Hydraulic system (Mechanism section) c. Function of negative brake (1) Negative brake function (Unload condition) No pressure is applied at the P-port, which means there is no piston driving force. In this state, the force of negative brake springs pushes down the negative brake piston to get the fric- tion plate between the piston and the casing.
  • Page 288 U20-3, U25-3 WSM Hydraulic system (Mechanism section) G.Rotary joint (Swivel joint) • Fixed undercarriage (U20-3, U25-3) PARTS NAME Q’ty Rotary joint assy Seal Seal Shaft Collor Collor Circlip Plug Plug (PT1/8) Plug (PT1/4) Plate Bolt Bolt Washer • Retractable undercarriage (U20-3) PARTS NAME Q’ty...
  • Page 289 U20-3, U25-3 WSM Hydraulic system (Mechanism section) • Fixed undercarriage (U20-3, U25-3) • Retractable undercarriage (U20-3) IV-M-38...
  • Page 290 U20-3, U25-3 WSM Hydraulic system (Mechanism section) H.Travel motor U20-3 (Fujikoshi) a. Structure & specifications • Specifications (Theoretical numbers) Type Displacements (1F/2F) cc/rev 16.1/8.4 Realuction gear ration 1/39 N·m 2156 Max. output torque kgf·m Max. output rpm (1F/2F) 36.6/70.2 IV-M-39...
  • Page 291 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. Principle of operation (1) Operating principle of wheel motor Description of operation The PHV series travelling motor has a stationary main body composed of a hydraulic motor and hydraulic valve and a rotating main body composed of a simple planetary gear reducer.
  • Page 292 U20-3, U25-3 WSM Hydraulic system (Mechanism section) [1] Reducer 1) Function The PHV series travelling motor reducer, which is a simple two-step planetary gear reducer, con- verts the high-speed revolution of the hydraulic motor to low-speed high torque to obtain case rotation.
  • Page 293 U20-3, U25-3 WSM Hydraulic system (Mechanism section) [2] Hydraulic motor 1) Function of motor The hydraulic motor, which is an axial piston motor (rotating cylinder and swash plate type), converts the hydraulic energy supplied from the pump to revolving movement.
  • Page 294 U20-3, U25-3 WSM Hydraulic system (Mechanism section) 3) Operating principle of two-speed motor The swash plate has two faces I and II on the surface opposite to the shoe-sliding surface and supported by the two balls fixed in the body 2 .
  • Page 295 U20-3, U25-3 WSM Hydraulic system (Mechanism section) [3] Hydraulic valve (counter balance valve) When the pressure oil is supplied through the port A, the pressure oil pushes open the check valve (3) and flows into the inlet-side port A’ of the hydraulic motor. At the same time, the pressure oil flows through the choke hole C into the room D and slides the spool valve (2) to the right, overcoming the force of spring (4).
  • Page 296 U20-3, U25-3 WSM Hydraulic system (Mechanism section) U25-3 (KAYABA) a. Structure & specifications IV-M-45...

  • Page 297: Specifications

    U20-3, U25-3 WSM Hydraulic system (Mechanism section) • Specifications Model Axial piston motor MAG-18V-230E-1 Reducer RGC-18V-43E-2 Axial piston motor 1st speed MAG equivalent capacity /rev 2nd speed 1st speed 18.0 Motor displacement /rev 2nd speed 10.0 Working pressure 21.6 Supply flow rate L/min 27.6...
  • Page 298 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. Operating principle of motor The cylinder block (7) incorporates nine piston S/As (14). The end face of the cylinder block (7) is in contact with the valve plate (21) having two semicircular ports B and C (high-low change valve).
  • Page 299 U20-3, U25-3 WSM Hydraulic system (Mechanism section) c. Operating principle of counter valance valve The counter balance valve is used to stop the axial piston motor and to prevent it from overrunning. When the control valve is in the neutral position, because no pressure is applied to the ports P1 and P2, the ports M1 and M2 (31-1) are blocked by the plunger and check valve (31-2) and therefore the motor does not rotate.
  • Page 300 U20-3, U25-3 WSM Hydraulic system (Mechanism section) • Counter balance function After the hydraulic oil discharged from the hydraulic pump is supplied to the port P1 of the counter valance valve via the control valve, the hydraulic oil passes through the check valve L (31-2) and flows through the port M1 into the piston motor, working to make the piston motor rotate.
  • Page 301 U20-3, U25-3 WSM Hydraulic system (Mechanism section) • Brake function When the control valve is returned to the neutral position, the pressure oil from the pump is shut off, the pressure in the ports P1 and P2 become the same, and the spring R (37) works to return the plunger (31- 1) to the neutral position.
  • Page 302 U20-3, U25-3 WSM Hydraulic system (Mechanism section) d. Function of Hi-Lo change • 1st (low) speed As shown in the figure, the swash plate (5) having three faces (a) to (c) is fitted to the flange holder through the two steel balls (6) so that it can be tilted.
  • Page 303 U20-3, U25-3 WSM Hydraulic system (Mechanism section) • 2nd (high) speed When the control valve is switched to the 2nd speed position, the pressure oil is supplied from the pump to the spool (41) and the spool is positioned as shown in the figure to the left. The motor driving pressure (P1: High pressure, P2: Low pressure) is supplied from the ports M1 and M2 through the ports Pi1 and Pi2 to the swash plate control piston (19).
  • Page 304 U20-3, U25-3 WSM Hydraulic system (Mechanism section) e. Function of reduction gear The reducer is composed of a two-step planetary gear mechanism. Construction view The drive gear [1] is engaged with the 1st planetary gear [2] and the 2nd sun gear [4] is engaged with the 2nd planetary gear [5].
  • Page 305 U20-3, U25-3 WSM Hydraulic system (Mechanism section) f. Function of anti-cavitation valve (1) Construction The anti-cavitation mechanism functions in sync with the counterbalance mechanism. Unlike conventional types of counterbalance mechanism, the oil passages A, B and C as well as the check valves B and C are added in this circuit.
  • Page 306 U20-3, U25-3 WSM Hydraulic system (Mechanism section) (2) Circuit behavior 1) Motor start-up When the hydraulic pressure is applied to P1, the counterbalance valve spool overcomes the spring’s counter-force and shifts to the right as shown in the figure below. In the meanwhile, the valve switches from M2 to P2, which gets the motor started.
  • Page 307 U20-3, U25-3 WSM Hydraulic system (Mechanism section) 2) Motor running at constant speed With the motor running at constant speed, the oil passage A stays under high pressure. Thanks to the action of the check valve C, however, the pressure oil is kept from leaking out toward the low- pressure side.
  • Page 308 U20-3, U25-3 WSM Hydraulic system (Mechanism section) 3) Motor slowing down When being slowed down, the motor keeps running for a while by its inertia force. While the coun- terbalance valve is open, however, the hydraulic oil flows through the oil passage M2 into the port Because there is no enough oil flow from P1, cavitation occurs at P1 and M1.
  • Page 309 U20-3, U25-3 WSM Hydraulic system (Mechanism section) 4) Motor stop The anti-cavitation function keeps on until the oil passage A and port P1 are shut off as shown in the figure below (at the indicated positions). IV-M-58...
  • Page 311 U20-3, U25-3 WSM Hydraulic system (Mechanism section) I. Hydraulic circuit diagram a. U20-3 Fixed undercarriage IV-M-59...
  • Page 312 U20-3, U25-3 WSM Hydraulic system (Mechanism section) b. U20-3 Retractable undercarriage IV-M-60...
  • Page 313 U20-3, U25-3 WSM Hydraulic system (Mechanism section) c. U25-3 IV-M-61...
  • Page 314 U20-3, U25-3 WSM Hydraulic system (Mechanism section) d. Hydraulic components layout U20-3, U25-3 (16) (18) (13) (14) (17) PART NAME Main pump Pilot value, L Pilot value, R Pilot filter Change valve Control valve Swivel motor Rotary joint Travel motor, L...
  • Page 315 U20-3, U25-3 WSM Hydraulic system (Service section) IV. Hydraulic system (Service section) A. Troubleshooting..........................IV-S-2 a. Common Circuit ........................IV-S-2 b. Hydraulics ..........................IV-S-4 c. Pump ............................IV-S-6 d. Motor ............................IV-S-7 e. Swivel performance .......................IV-S-8 f. Traveling performance ......................IV-S-14 B. Specifications ..........................IV-S-18 a.
  • Page 317 U20-3, U25-3 WSM Hydraulic system (Service section) A.Troubleshooting a. Common Circuit Engine The starter does not function. Check the electrical system. The engine fails to start. The starter functions, but the engine fails to start. Check the engine. Check the hydraulic system.
  • Page 318 U20-3, U25-3 WSM Hydraulic system (Service section) The engine’s maximum rpm is unusual. Check the engine. Check the front system. The entire hydraulic system responds too slow or too weak. Any of the boom, arm, bucket, swing and dozer The hydraulic Check the front system.
  • Page 319 U20-3, U25-3 WSM Hydraulic system (Service section) b. Hydraulics Problem Cause Correction (1) Hydraulic oil too short in the tank or oil Add or change the hydraulic oil. degraded. Check the suction line and replace the The entire hydraulic system fails (2) Suction line (suction filter) clogged.
  • Page 320 U20-3, U25-3 WSM Hydraulic system (Service section) Problem Cause Correction Check the pedal and link and readjust as (1) Swing pedal and link maladjusted. required. (2) Control valve swing section spool Check the spool and repair as required. The swing mechanism alone malfunctioning.
  • Page 321 U20-3, U25-3 WSM Hydraulic system (Service section) c. Pump Problem Cause Correction 1) Engine rpm higher than specified. 1) Readjust as specified. 1. The engine gets overloaded. 2) Pressure higher than specified. 2) Readjust as specified. 3) Pump internal parts seized or damaged.
  • Page 322 U20-3, U25-3 WSM Hydraulic system (Service section) d. Motor Problem Cause Correction No pressure rise or no oil flow. Check the entire hydraulic circuit including the valves and pumps. Oil viscosity inappropriate. Ensure the specified viscosity ranges. Motor failure Dust, degraded hydraulic oil, cavitation, Run the motor alone and get it under a pressure of 30 kgf/cm (2.9...
  • Page 323 U20-3, U25-3 WSM Hydraulic system (Service section) e. Swivel performance First make sure the swivel mechanism alone is in trouble. Problem Cause Correction Check the performance. Overhaul (2) Pilot valve spool malfunctioning and clean. Check the performance. Overhaul (3) Control valve spool stick malfunctioning and clean.
  • Page 324 U20-3, U25-3 WSM Hydraulic system (Service section) Problem Cause Correction Check the performance. Overhaul (3) Control valve spool malfunctioning and clean. Check the performance. Overhaul (7) Anti-void valve malfunctioning, valve seat defective Wobbling if pressed by and clean. hand Measure the pressure. Overhaul, (6) Brake valve pressure unspecified clean and readjust.
  • Page 325 U20-3, U25-3 WSM Hydraulic system (Service section) 1) Swivel mechanism check points 1. First make sure the swivel mechanism alone is in trouble. 2. Then see if what is in trouble is in both directions or in either direction. 3. Also see if the trouble occurs all the time or from time to time and how often it happens.
  • Page 326 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Checking the pilot valve spool performance 1. Operate the swivel lever and see if the pilot valve spool functions well. 2. If the spool malfunctions, check for foreign matters, scratches, deformation, etc.
  • Page 327 U20-3, U25-3 WSM Hydraulic system (Service section) 5) Checking the brake release 1. Measure the pressure between the solenoid valve and the swivel motor brake. 2. Make sure the pressure is as specified. 3. Start the engine and unlock the control lever.
  • Page 328 U20-3, U25-3 WSM Hydraulic system (Service section) 7) Checking the anti-void valve and valve seat 1. Check the anti-void valve for heavy movement, scratches, foreign matters, etc. Prepare an 8M hex hollow wrench that is 45 mm or so tall.
  • Page 329 U20-3, U25-3 WSM Hydraulic system (Service section) f. Traveling performance In advance, make sure the trouble is in the travel mechanism alone. Problem Cause Correction Failure to run. (1) Travel lever linkage stuck or missing. Readjust the linkage or replace as required.
  • Page 330 U20-3, U25-3 WSM Hydraulic system (Service section) 1) Travel mechanism check points IV-S-15...
  • Page 331 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Checking the communicating valve 1. For disassembling and reassembling the control valve, refer to IV-S-63. 2. Remove the cap and spool. Check and clean them up. 3. Clean up the filter in the cap too.
  • Page 332 U20-3, U25-3 WSM Hydraulic system (Service section) 4) Checking the rotary joint for internal leak Checking the left travel 1. Make sure there is nothing unusual between the pump and rotary joint. 2. Disconnect the *-marked hoses as shown at left.
  • Page 333 U20-3, U25-3 WSM Hydraulic system (Service section) B.Specifications a. Pomp [1] Specifications Unit U20-3 U25-3 Remarks Manufactue Industry Co.Ltd Model PVD-08-24P-6G3 PVD-08-24P-8G3 Rated pump rpm 2,200 2,400 P1, P2 21.6 21.6 Main relief kgf/cm pressure Rated load pressure 20.6 17.2...
  • Page 334 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Piston pump P-Q performance curve (Theoretical) U-20-3 (l/min) l/min 10cc/rev =240kgf/cm 10.45cc/rev =210kgf/cm =5kgf/cm 23.0 7cc/rev Measuring conditions 22.0 =350kgf/cm 10.3cc/rev Oil used ISO VG46 or equivalent 5.2cc/rev =100kgf/cm Oil temperature 50 5 C...
  • Page 335 [1] Relief valve (bench data) Valve location Operating work Unit U20-3 U25-3 Remarks 21.6 21.6 U20-3: at 29 L/min Bucket crowd Main relief valve kgf/cm U25-3: at 29 L/min Arm crowd or 21.6 21.6 U20-3: at 29 L/min Main relief valve...
  • Page 336 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Main relief valve (at the measurement port on the machine) Valve location Operating work Unit U20-3 U25-3 Remarks +1.0 +1.0 22.1 22.1 -0.5 -0.5 Bucket crowd Main relief valve kgf/cm Arm crowd or 22.1...
  • Page 337 Eaton Fluid Power Eaton Fluid Power Model 25PB2PA 25PB25A1125-C Displacement cc/rev Max. oil flow L/min Rated flowrate U20-3: at 12.4 L/min Motor speed 63.4 75.4 U20-3: at 18.4 L/min 19.6 16.2 Brake valve pressure kg/cm Drain amount at lock L/min...
  • Page 338 U20-3, U25-3 WSM Hydraulic system (Service section) d. Traveling performance U20-3 U25-3 Remarks Manufacturer Fujikoshi KAYABA Model PHV-190-39-1 MAG-18V-230E Capacity 1st/2nd cc/rev 16.1/8.4 18.0/10.0 Reduction ratio 1/39 1/42.96 Total displacement cc/rev 627.9/327.6 774/430 Rated oil flow L/min 27.6 kg·m 269.6 N·m...
  • Page 339 U20-3, U25-3 WSM Hydraulic system (Service section) e. Cylinder [1] Speed U20-3 U25-3 Unit Remarks Canopy sec. 2.5~3.1 2.1~2.7 GL to Max. height Boom cylinder (exclude cushion time) Cabin sec. 2.1~2.7 2.1~2.7 Canopy sec. 2.6~3.2 2.4~3.0 Boom cylinder Down Max. height to GL Cabin sec.
  • Page 340 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Specifications and dimensions 1) Specifications and dimensions at a glance Unit U20-3 U25-3 Remarks Tube I.D. × Rod O.D. 65×35 70×40 Stroke 482/452 476/455 canopy/cabin Max.retraction length 778/778 795/795 canopy/cabin Seal Kit No.
  • Page 341 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Cylinder dimensional specifications U20-3 Unit Port screw size Remarks Boom Bucket Swing Dozer U25-3 Unit Port screw size Remarks Boom Bucket Swing Dozer IV-S-26...
  • Page 342 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Tightening torque 1. Boom cylinder N·m Tightening torque ( Thread size kgf·m Adhesive U20-3 U25-3 U20-3 U25-3 Cylinder head M72×2 M77×2 Three bond # 1901 35.0 39.0 Piston M27×2 M30×2 59.0 76.2 16.2...
  • Page 343 U20-3, U25-3 WSM Hydraulic system (Service section) 4. Dozer cylinder N·m Tightening torque ( Thread size kgf·m Adhesive U20-3 U25-3 U20-3 U25-3 Cylinder head M87×2 M97×2 Three bond # 1901 46.0 54.1 Piston M33×2 M36×3 81.1 87.2 16.2 16.2 Set screw M8×1.25...
  • Page 344 U20-3, U25-3 WSM Hydraulic system (Service section) C.Testing a. Pump flow 1) Measuring procedure 1. Connect the tester to the pump outlet. Be careful not to confuse the tester’s pipe connections. 2. Open the tester’s loading valve. Start the engine.
  • Page 345 U20-3, U25-3 WSM Hydraulic system (Service section) Control valve section layout (1) Rod (2) Bottom (3) Communicating valve (4) Dozer (5) Swing (6) Swivel (7) Spare (8) Arm (9) Travel left (10) Travel right (11) Boom (12) Bucket b. Pressure measurement...
  • Page 346 U20-3, U25-3 WSM Hydraulic system (Service section) Control valve section layout Pilot valve hose routes Left pilot valve Right pilot valve Back Back Front Front Left pilot valve Right pilot valve Location Hose tape color Location Hose tape color Swivel left...
  • Page 347 U20-3, U25-3 WSM Hydraulic system (Service section) Control valve section layout (1) Rod (2) Bottom (3) Communicating valve (4) Dozer (5) Swing (6) Swivel (7) Spare (8) Arm (9) Travel left (10) Travel right (11) Boom (12) Bucket 2) Adjusting procedure 1.
  • Page 348 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Overload relief pressure Pump discharge side 1) Measuring procedure (in tucking in the arm) 1. Remove the adaptor plug (2) (1/8) of main pump discharge side and connect thereto a pressured gauge.
  • Page 349 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Adjusting procedure 1. Loosen the lock nut of the overload relief valve, turn the adjusting screw with a hex wrench to set the pressure and tighten the lock nut after setting. 2. With the engine running at maximum rpm, operate the lever and check the set pressure.
  • Page 350 U20-3, U25-3 WSM Hydraulic system (Service section) [5] Swivel brake release valve 1) Measuring procedure 1. Stop the engine, disconnect the swivel brake release hose of the selector valve using a vacuum pump and set the pressure gauge. 2. With the engine running at maximum rpm, unlock the lever (to bring it to operating position) and measure the pressure.
  • Page 351 U20-3, U25-3 WSM Hydraulic system (Service section) c. Drain measurement [1] Travel motor 1) Measuring procedure 1. Disconnect the drain hose of the travel motor and plug the drain hose to prevent oil from flowing out of the tank. 2. Connect another hose (a vinyl hose for low pressure will do) to the travel motor drain port.
  • Page 352 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Swivel motor 2) Measuring procedure 1. Disconnect the drain hose using the vacuum pump as shown in the photo. 2. Plug the tank-side hose which has been disconnected. 3. Dismount the vacuum pump.
  • Page 353 U20-3, U25-3 WSM Hydraulic system (Service section) d. Measurement of block performance [1] Swivel 1) Measuring procedure 1. Park the machine on a 20-degree slope. 2. Bring the front attachments into such a posture that the arm is ready for dumping and the bucket is crowded, and hold the boom in line with the boom root pin and bucket pin.
  • Page 354 U20-3, U25-3 WSM Hydraulic system (Service section) e. Operating speed [Points] (1) Measure the time required for full stroke with the standard front attachments without load. (2) Repeat the measurement several times, obtain the average and adopt it as measured value.
  • Page 355 U20-3, U25-3 WSM Hydraulic system (Service section) 4) Bucket cylinder 1. Bring the boom and arm into the postures as shown in the figure. 2. Operate the engine at maximum rpm. 3. Measure the time required for full stroke of the bucket cylinder.
  • Page 356 U20-3, U25-3 WSM Hydraulic system (Service section) 8) Travel 1. Bring the machine into traveling posture and run up the machine until each speed reaches the maximum. 2. Measure the time required for travel in 10 m distance. (1) Run-up...
  • Page 357 1. Locate the machine on the flat ground, and put the load the bucket. Load on the bucket should be as follows. U20-3: 280 kg - include bucket weight 620 lbs - include bucket weight U25-3: 285 kg - include bucket weight 2.
  • Page 358 U20-3, U25-3 WSM Hydraulic system (Service section) D.Disassembling and Assembling a. Pump [1] Pump coupling 1) Disassembling the pump 1. Bring the attachments down to the ground and stop the engine. 2. Open the bonnet, remove the bonnet left cover and dismount the muffler.
  • Page 359 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Reassembling procedure 1. Apply an appropriate amount of grease to the spline before mounting the pump. CAUTION: Do not allow grease onto the rubber parts. Rubber may be deteriorated. 2. Tightening torque of coupling mounting bolt: 48.1-55.9N⋅m(4.9 ~ 5.7kgf⋅m)
  • Page 360 [2] Mounting and dismounting the pump Filter Nameplate U20-3 EU: Blue U25-3 EU: Yellow Identification of pumps [Note] Both the U20-3 EU and U25-3 Color of nameplate EU have side branches. U20-3 EU Blue U25-3 EU Yellow 2) Reassembling procedure 1.
  • Page 361 U20-3, U25-3 WSM Hydraulic system (Service section) [3]Component parts of pump Fig. 2 Construction of Hydraulic Pump Part name Q’ty No. Part name Q’ty No. Part name Q’ty No. Part name Q’ty Body S 21 Rod G 41 None 61 Hex nut...
  • Page 362 U20-3, U25-3 WSM Hydraulic system (Service section) [4]Disassembling and reassembling the pump. General precautions After draining the oil out of the pump, first clean up the pump. Lay clean paper, cloth or rubber sheet on the workbench and place the pump on them. Disassembly and reassemble the pump with care using necessary tools.
  • Page 363 U20-3, U25-3 WSM Hydraulic system (Service section) 3. Separating the body S from the body H Remove the upper two of the five M10x35 hex socket bolts (44). Tool: Hex wrench 8 mm Temporarily tighten the two M10x65 bolts about 10 mm deep to this position and slowly tighten the remaining three bolts.
  • Page 364 U20-3, U25-3 WSM Hydraulic system (Service section) Using a plastic hammer, tap on the opposite end of the shaft, and the oil seal (32) and the shaft (with bearing (30)) can be removed. 6. Disassembling the body H kit When the hex socket lock screw (60) is...
  • Page 365 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Reassembling Reassembling precautions The parts are reassembled in the reverse order of being disassembled. Wash the parts with clean washing oil and handle them with due care not to allow dust deposits and foreign matters as well as not to damage the sliding faces of parts during assembly work.
  • Page 366 U20-3, U25-3 WSM Hydraulic system (Service section) 3. Assembling the stopper pin A and B kits Assemble the two plate springs (33) to the stopper pin A (25) to form the stopper pin A kit. Similarly, assemble the two plate springs (33) to the stopper pin B (26) to form the stopper pin B kit.
  • Page 367 U20-3, U25-3 WSM Hydraulic system (Service section) 7. Mounting the hex socket lock screw Secure the hex socket lock screw (60) and the hex nut (61) to achieve the same length as before disassembly. (Wrench “13”, hex wrench “4”) 8. Mounting the gear pump...
  • Page 368 U20-3, U25-3 WSM Hydraulic system (Service section) b. Control valve [1] Mounting and dismounting the valve Identification of control valve * The U25-3 EU Marking Color of marking nameplate is U20-3 EU: Blue colored red. U20-3 EU Blue U25-3 EU: None...
  • Page 369 U20-3, U25-3 WSM Hydraulic system (Service section) Part No. Part name Q’ty Remarks Bolt Plain washer U25-3 EU (None) Bolt Bolt Snap pin Rod (130) Plain washer Dozer Snap pin Rod (190) Plain washer Snap pin Service port spec. Snap pin...
  • Page 370 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Disassembling and reassembling Specification the valve Model KVSE-36-10 Kayaba Industry Co., Maker Ltd. Weight Approx. 31 kg Tightening torque of tie rod 26.5 ~ 29.4 N·m IV-S-55...
  • Page 371 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Component parts of sections 1) Bucket section Component parts (1) Poppet (2) Poppet Overload relief valve (A) Spring seat (B) O-ring (C) Spring seat (D) Spring 2) Boom section Component parts (3) Poppet...
  • Page 372 U20-3, U25-3 WSM Hydraulic system (Service section) Component parts of anti-drift valve (1) Plug assembly (2) Piston (3) Spring (4) Plug (5) Spool (6) Sleeve (7) Poppet (8) Spring seat (9) Spring Tightening torque of plug assembly (1): 69 ~78 N⋅m...
  • Page 373 U20-3, U25-3 WSM Hydraulic system (Service section) 4) Inlet section Component parts a1 Main relief valve (1) O-ring Component part of main relief valve (1) Adjuster, washer (6) Spring (2) Nut (7) Piston (3) Spring (8) Sleeve (4) Pilot poppet...
  • Page 374 U20-3, U25-3 WSM Hydraulic system (Service section) 5) Travel left section Component parts (E) Cap screw (F) Spring (G) Wiper (H) O-ring ( I ) O-ring (7) Poppet, spring IV-S-59...
  • Page 375 U20-3, U25-3 WSM Hydraulic system (Service section) 6) Arm section Component parts (8) Poppet Overload relief valve Overload relief valve (A) Spring seat (B) O-ring (C) Spring seat (D) Spring (E) O-ring 7) Service port section Component parts (9) Poppet...
  • Page 376 U20-3, U25-3 WSM Hydraulic system (Service section) (12)Poppet, spring 9) Swing section Component parts (13)Poppet (14)Anti-void valve (E) Cap screw (F) Spring (G) Wiper (H) O-ring ( I ) O-ring Component parts of anti-void valve (1) Cap (2) Sleeve (3) Spring...
  • Page 377 U20-3, U25-3 WSM Hydraulic system (Service section) 10) Dozer section Component parts (15)Poppet Overload relief valve (E) Cap screw (F) Spring (G) Wiper (H) O-ring ( I ) O-ring Component parts of overload relief valve (1) Adjuster, nut, washer (6) Spring...
  • Page 378 U20-3, U25-3 WSM Hydraulic system (Service section) 12) Communicating valve Component parts a2 Main relief valve (A) Spring seat (B) O-ring (C) Spring seat (D) Spring IV-S-63...
  • Page 379 U20-3, U25-3 WSM Hydraulic system (Service section) C. Pilot valve 1) Reassembling procedure [1] Mounting and dismounting the pilot 1. Tightening torque of grip lock nut: 25.0~27.0 valve N-m (2.5~2.8 kgf⋅m) The stepped (machined) part should be toward the lever.
  • Page 380 U20-3, U25-3 WSM Hydraulic system (Service section) Left P/V Right P/V Back Back Back Front Front Front Part No. Part name Q’ty Maker Remarks Kawasaki Heavy Ind- RC417-61711 Valve, assembly (Pilot L) (652) made. Kawasaki Heavy Ind- RC417-61721 Valve, assembly (Pilot R)
  • Page 381 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Disassembling and reassembling the pilot valve 1) Tools and tightening torque Tightening torque Tool Size (mm) Part No. Part name Screw size (N·m) Hex wrench Hex socket bolt 20.6 ± 1.5 Adjusting nut Money wrench 68.6 ±...
  • Page 382 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Disassembling 1. Preparations (1) Prepare a workbench that is spacious enough for the parts handled and strong and stable enough to keep the parts in place. (2) Also have the tools and jigs, discussed in Item 7-1, at hand.
  • Page 383 U20-3, U25-3 WSM Hydraulic system (Service section) Procedure Precautions Remove the folding-purpose spring (246) and spring seat (218) from the push rod (212). [Photo 7-16] Draw the push rod (212) out of the plug (211). [Photo 7-17] Remove the O-ring (214) and seal (213) from the plug (211).
  • Page 384 U20-3, U25-3 WSM Hydraulic system (Service section) 4) Assembling 1. Preparations (1) As in the case of disassembling, prepare the specified workbench, tools and materials. 2. General precautions (1) Take the same general precautions as in disassembling. (2) Before reassembling, remove metal chippings and foreign matters from all the parts. Make sure the parts are free of burrs, hit marks and other problems.
  • Page 385 U20-3, U25-3 WSM Hydraulic system (Service section) Procedure Precautions Fit the plug assembly to the casing (101). * Be careful not to pry the spool (201) too hard. When the return spring (221) is weak in force, this Otherwise the casing hole (101) may get damaged.
  • Page 386 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-1 Photo 7-2 Photo 7-3 Photo 7-4 Photo 7-5 Photo 7-6 IV-S-71...
  • Page 387 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-7 Photo 7-8 Photo 7-9 Photo 7-10 Photo 7-11 Photo 7-12 IV-S-72...
  • Page 388 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-13 Photo 7-14 Photo 7-15 Photo 7-16 Photo 7-17 Photo 7-18 IV-S-73...
  • Page 389 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-19 Photo 7-20 Photo 7-21 Photo 7-22 Photo 7-23 Photo 7-24 IV-S-74...
  • Page 390 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-25 Photo 7-26 Photo 7-27 Photo 7-28 Photo 7-29 Photo 7-30 IV-S-75...
  • Page 391 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-31 Photo 7-32 Photo 7-33 Photo 7-34 Photo 7-35 Photo 7-36 IV-S-76...
  • Page 392 U20-3, U25-3 WSM Hydraulic system (Service section) Photo 7-37 Photo 7-38 [3] Trouble shooting It is not easy to pinpoint trouble spots. The table below lists some typical problems, their possible causes and corrections. Before starting repair jobs, refer to the table below.
  • Page 393 U20-3, U25-3 WSM Hydraulic system (Service section) d. Swivel motor [1] Mounting and dismounting the swivel motor 1) Dismounting the swivel motor 1. Let out the hydraulic oil. 2. Remove the steps. 3. Remove the related wire harnesses for dismounting the seat stand.
  • Page 394 U20-3, U25-3 WSM Hydraulic system (Service section) 13. Remove the 4 motor mounting bolts. Tightening torque: 103.0 ~117.7 N⋅m (10.5 ~ 12.0 kgf⋅m) Apply screw loctite. (Loctite 271) 14. Dismount the motor. IV-S-79...
  • Page 395 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Swivel motor mounting/dismounting component parts 2) Reassembling procedure (1) Drain hose (to tank) (2) To right and left control valves (3) For negative brake releasing (to selector valve) (4) Brake valve (5) Anti-void valve Part No.
  • Page 396 U20-3, U25-3 WSM Hydraulic system (Service section) Part name Part No. Q ty Remarks Pinion gear assembly AD1165C Including 1 ~ 22 Bearing housing Flange mounting Pinion gear Plug Rc1/8 Collar Ring gear Snap ring for shaft Piston Ring Friction plate...
  • Page 397 U20-3, U25-3 WSM Hydraulic system (Service section) IV-S-82...
  • Page 398 U20-3, U25-3 WSM Hydraulic system (Service section) Part name Q'ty Part No. Remarks 1 Valve body 2 Plunger 3 Seat 4 Piston 5 M27 plug 6 O-ring A40001-24 1BP24 7 Seal set AH0597A 8 Orifice plug φ0.40 φ0.35 9 Orifice plug...
  • Page 399 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Disassembling and reassembling the swivel motor 1) Disassembling/reassembling tools Wash the parts with clean oil and remove dust and Torque wrench: 9.8~98 N⋅m dirt off them. Also use due care not to give damage Socket wrench: 14 mm or dent to them.
  • Page 400 U20-3, U25-3 WSM Hydraulic system (Service section) 3. Dismount the valve housing. At this time, use care not to lose the spring. Do not disassemble the valve housing unless necessary. 4. Remove the balancing ring, valve and valve seat. 5. Remove the valve drive and geroller.
  • Page 401 U20-3, U25-3 WSM Hydraulic system (Service section) 7. When the pinion gear must be disassembled, take the following. (1) Dismount the bearing housing. (2) Remove the 8 springs. 8. Remove the piston. The piston will be easily removed by blowing air through the brake release port.
  • Page 402 U20-3, U25-3 WSM Hydraulic system (Service section) 11. Remove the snap ring for shaft. Bear in mind that the snap ring may pop out. 12. Remove the snap ring for hole. Bear in mind that the snap ring may pop out.
  • Page 403 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Reassembling procedure Reassemble the parts after washing and checking them for any damage. 15. Apply hydraulic oil to the X-ring before mounting. 16. Mount the pinion gear and the snap rings for hole and shaft.
  • Page 404 U20-3, U25-3 WSM Hydraulic system (Service section) 18. Check the inner and outer O-rings of the ring for scratches and distortion, and apply hydraulic oil to them before assembling. 19. Check the outer O-ring of the piston for scratches and distortion, and apply hydraulic oil to it before assembling.
  • Page 405 U20-3, U25-3 WSM Hydraulic system (Service section) 22. Mount the geroller. Align it with the drain hole. 23. Insert the valve drive. 24. Fit the 2 different O-rings into the O-ring grooves of the valve plate. Mount the valve plate onto the geroller.
  • Page 406 U20-3, U25-3 WSM Hydraulic system (Service section) 25. Mount the valve. 26. Mounting the valve is important for determining the motor rotating direction. Mount it with care according to the left figure. Wrong timing will rotate the motor in the wrong direction, which causes danger.
  • Page 407 U20-3, U25-3 WSM Hydraulic system (Service section) 28. Fit the 2 different O-rings into the O-ring grooves of the valve housing. Insert a screwdriver or the like from the B port of valve housing, and mount the valve housing to the valve while holding the balancing ring in place.
  • Page 408 U20-3, U25-3 WSM Hydraulic system (Service section) 30. Fit the steel ball, spring and check plug to the valve housing. Tightening torque: 59 N⋅m (6 kgf⋅m) Now the swivel motor has been reassembled. Before mounting it to the machine, check the motor rotating direction.
  • Page 409 U20-3, U25-3 WSM Hydraulic system (Service section) e. Rotary joint (Swivel joint) 1) Mounting and dismounting procedure 1. Let out the hydraulic oil. 2. Dismount the steps. 3. Disconnect the return, bucket and boom hoses from the control valve. 4. Disconnect the travel, dozer, 2-speed select and drain hoses.
  • Page 410 U20-3, U25-3 WSM Hydraulic system (Service section) 7. Remove the 4 lock bolts. (Place a jack below the machine or apply ropes or the like to the machine to avoid a fall.) Tightening torque of swivel joint assembly and track frame: 166.7~196.1 N⋅m (17.0~20.0 kgf⋅m)
  • Page 411 U20-3, U25-3 WSM Hydraulic system (Service section) Insert the seal ring using a specific tool. Seal inserting tool Tool No.: KS000-00130 IV-S-96...
  • Page 412 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Mounting the adaptor 1. Mount the adaptor as shown in the figure and photo. 2. Tightening torque of hydraulic adaptor: G1/4 24.5 ~ 28.4 N⋅m (2.5~3.0 kgf⋅m) G3/8 49.0 ~ 53.9 N⋅m (5.0~5.5 kgf⋅m) 3.
  • Page 413 U20-3, U25-3 WSM Hydraulic system (Service section) f. Traveling motor [1] Mounting and dismounting the wheel motor 1) Mounting and dismounting the wheel motor 1. Loosen the tension cylinder and remove the crawler CAUTION: If you work together with a person to remove the crawler, pay attention to the positions of your and the person’s feet and hands.
  • Page 414 U20-3, U25-3 WSM Hydraulic system (Service section) [2] List of adapter hoses Parts list Part No. Part name Q’ty Remarks RB511-1443Δ Drive sprocket (111) 01128-61025 Bolt M10✕ 1.5 RB511-6129Δ Motor assembly (wheel) Kayaba-made (614) 01128-61025 Bolt M10✕ 1.5 68311-6432Δ Straight pipe joint •...
  • Page 415 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Component parts of wheel motor IV-S-100...
  • Page 416 U20-3, U25-3 WSM Hydraulic system (Service section) Parts list Part No. Name Q’ty Part No. Name Q’ty Spring Reducer Valve plate Flange holder Floating seal Ball bearing Angular bearing O-ring Ring nut O-ring Plug Base plate Housing Spool assembly Steel ball...
  • Page 417 U20-3, U25-3 WSM Hydraulic system (Service section) [4] Disassembling and reassembling the wheel motor 1) General cautions in disassembling/reassembling In disassembling and reassembling, observe the following precautions. 1. Perform work in a clean place and take care not to allow dirt, dust, paint flakes, water, etc. to adhere to the motor.
  • Page 418 U20-3, U25-3 WSM Hydraulic system (Service section) 3. Insert the two-speed spool and spring into the body 1. 4. Tighten the plug (both sides) to which the O- ring is fitted. Tightening torque of plug:46~51 N⋅m (4.7~5.3 kgf⋅m) Take care that the spool and spring are positioned and oriented properly.
  • Page 419 U20-3, U25-3 WSM Hydraulic system (Service section) 6. Tighten the plug (both sides) to which the O- ring is fitted. Tightening torque of plug:12~22 N⋅m (1.2~2.3 kgf⋅m) Width across flat of hexagon: 5 mm 7. Press-fit the bearing and spring pin into the body 1.
  • Page 420 U20-3, U25-3 WSM Hydraulic system (Service section) 9. Fit the parallel pin to the body 2. 10. Press-fit the bearing onto the shaft. CAUTION: The bearing cannot be disassembled because it is press-fitted. 11. Fit the control piston, steel ball and shaft to the body 2.
  • Page 421 U20-3, U25-3 WSM Hydraulic system (Service section) 12. Fit the swash plate. 13. Fit the retainer, spring and retainer to the cylinder barrel in this order and fix them with the snap ring. IV-S-106...
  • Page 422 U20-3, U25-3 WSM Hydraulic system (Service section) 14. Insert the pins (3 pairs) into the cylinder barrel. CAUTION: Take care not to lose the pin at the time of disassembling/assembling. 15. Fit the retainer holder to the cylinder barrel. 16. Using the shoe holder assembly and barrel holder, assemble the cylinder barrel assembly.
  • Page 423 U20-3, U25-3 WSM Hydraulic system (Service section) 18. Fit the valve plate to the body 1. 1) Apply hydraulic oil to the sliding surface (copper surface) of the valve plate. 2) Applying grease to the back surface (iron surface) of the valve plate will prevent it from coming off easily.
  • Page 424 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Reassembling the reducer 1. Fit the bearing to the main body. 2. Fit the snap ring for hole. 3. Fit the bearing. 4. Fit the floating seat combined with the O-ring. If it is difficult to fit it, apply grease to the O- ring.
  • Page 425 U20-3, U25-3 WSM Hydraulic system (Service section) 5. Fit the floating seat combined with the O-ring to the hydraulic motor. If it is difficult to fit it, apply grease to the O- ring. 6. Combine the main body and the hydraulic motor and fix them with the snap ring.
  • Page 426 U20-3, U25-3 WSM Hydraulic system (Service section) 7. Fit the ring, thrust washer, gear b1 and needle to the body 2 in this order. 8. Fit the thrust plate 1 and fix it with the snap ring. CAUTION: Fit the plate with the convex surface of the inside diameter side faced upward.
  • Page 427 U20-3, U25-3 WSM Hydraulic system (Service section) 11. Fit the gear b2 and needle to the carrier II in this order. 12. Fit the gear S2. 13. Fit the thrust plate II and fix it with the snap ring to assemble the carrier II assembly.
  • Page 428 U20-3, U25-3 WSM Hydraulic system (Service section) 15. Fit the O-ring to the main body. 16. Inject 0.33L of lubricating oil. 17. Fit the cover to the main body. 1) Apply grease to the O-ring and fit the cover horizontally while taking care not to damage it.
  • Page 429 U20-3, U25-3 WSM Hydraulic system (Service section) 19. Fit the flanged plug (G3/8) to which the O-ring is fitted. CAUTION: 1. As shown in the figure below, use the flange of the plug to prevent the cover from turning. Tightening torque: 46 ~ 51 N⋅m (4.7 ~ 5.2 kgf⋅m) Width across flat of hexagon: 8 mm 20.
  • Page 430 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Reassembling the wheel motor 1. Fit the floating seal 1) Temporarily set the floating seal using the guide jig (see the figure below). (1) Floating seal (2) Flange holder (3) Guide jig 2) Fit the floating seal using the mounting jig (see the figure below).
  • Page 431 U20-3, U25-3 WSM Hydraulic system (Service section) 4. Using the tightening jig, tighten the ring nut so as to leave no clearance between the ring nut and angular bearing. • For the tightening jig, refer to V17. (1) Ring nut (2) Tightening jig 5.
  • Page 432 U20-3, U25-3 WSM Hydraulic system (Service section) 8. Using a punch, crimp the plug at two points in order to prevent it from getting loose. 9. Put the steel balls in the unit. (1) Steel ball • Number of steel balls 10.
  • Page 433 U20-3, U25-3 WSM Hydraulic system (Service section) 12. Attach the thrust plate, and apply loctite No. 262 to the flush screw and tighten it. • When applying loctite, well degrease the part and use a hardening accelerator. • Tightening torque of screw: 0.41~ 0.83 kgf⋅m...
  • Page 434 U20-3, U25-3 WSM Hydraulic system (Service section) 18. Bend the wire at a point about 8 mm apart from the end, insert it into the screw hole in the housing, and turn the cover to draw the wire into the housing.
  • Page 435 U20-3, U25-3 WSM Hydraulic system (Service section) 23. Fit the steel ball, spring, piston subassembly and swash plate to the flange holder. • Apply hydraulic oil to the sliding surface of the swash plate. (1) Swash plate 24. Attach the collar, spring and washer to the cylinder block and fit the snap ring using the mounting jig (see the figure below).
  • Page 436 U20-3, U25-3 WSM Hydraulic system (Service section) 27. Set the motor on its side and fit the cylinder block subassembly using the spline in the shaft as a guide. 28. While pushing the cylinder block by hand, check that the spring works.
  • Page 437 U20-3, U25-3 WSM Hydraulic system (Service section) 30. Press-fit the ball bearing into the base plate using the press-fitting jig (see the figure below). 31. Fit the pin and crimp it at two at two points. 32. Apply grease to the back surface of the valve plate and fit it to the base plate.
  • Page 438 U20-3, U25-3 WSM Hydraulic system (Service section) 33. Fit the base plate and tighten the socket head bolt. • Tightening torque of socket head bolt: 37.0±1.9 N⋅m IV-S-123...
  • Page 439 U20-3, U25-3 WSM Hydraulic system (Service section) 34. Fit the check valve and spring to the plunger. 35. Attach the O-ring to the plug and fit the plug to the plunger. • Tightening torque of plug: 27.0±2.45 N⋅m (1) Plunger assembly 36.
  • Page 440 U20-3, U25-3 WSM Hydraulic system (Service section) 39. Attach the spring to the spool and fit the spool to the base plate. • Apply hydraulic oil to the spool and insert it while turning it. 40. Attach the O-ring to the plug and fit the plug to the base plate.
  • Page 441 U20-3, U25-3 WSM Hydraulic system (Service section) 42. Fit the valve assembly to the base plate. • Tightening torque: 15.2±0.8 N⋅m 43. Fit the check valve and spring to the valve body. 44. Tighten the plug. • Tightening torque of plug: 36.8±2.5 N⋅m...
  • Page 442 U20-3, U25-3 WSM Hydraulic system (Service section) 45. Attach the O-ring to the plug and fit the plug to the base plate. • Tightening torque of plug: 22.6±1.0 N⋅m (1) Cap (2) Plug 46. Inject the specified amount of gear oil (see below) through the plug screw hole and tighten the plug.
  • Page 443 U20-3, U25-3 WSM Hydraulic system (Service section) b. Cylinder [1] Disassembling and reassembling the boom cylinder 1) Drain oil from the cylinder. 2) Fix the cylinder with a vise. Supplement: Support the cylinder tube with a wooden board. 3) Straighten the lock washer.
  • Page 444 U20-3, U25-3 WSM Hydraulic system (Service section) 5) Pull out the piston rod together with the cylinder head. Supplement: Open the port of the pipe. Caution: When pulling out the piston, take care not to drop the piston end. If the piston end drops, it could injure your hand or damage the piston itself.
  • Page 445 U20-3, U25-3 WSM Hydraulic system (Service section) 7) Fix the piston rod with a vise. IMPORTANT Support the rod with a wooden board. (8) Vise (9) Wooden board 8) Set a spanner on the hex nut portion of the piston and loosen the piston.
  • Page 446 U20-3, U25-3 WSM Hydraulic system (Service section) 10) Remove the cushion bearing and holder. 11) Pull out the cylinder head. Release the piston rod from the vise. [2] Component parts of boom cylinder (1) Cylinder tube (2) Piston rod (3) Piston (4) Cushion bearing (5) Holder...
  • Page 447 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Measuring the bent in the piston rod 1. Place the piston rod on a V block. 2. Put a dial gauge on the center of the rod. 3. While turning the piston rod, read the value indicated by the dial gauge.
  • Page 448 U20-3, U25-3 WSM Hydraulic system (Service section) h. Hydraulic hose (Important) The hydraulic hose (main pump suction/delivery) should be replaced [1] Delivery hose every two years or 400 hours of operation, whichever is earlier. 1) Delivery hose routing [2] Delivery hose routing...
  • Page 449 U20-3, U25-3 WSM Hydraulic system (Service section) [2] Return drain hose 1) Return drain hose routing 2) Return drain hose routing IV-S-134...
  • Page 450 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Return drain hose routing Hydraulic tank Swivel joint Back Back Front Front Return valve Pilot valve (left) Pilot valve (right) Control valve Bottom Left Backward Backward Bottom Boom Low-pressure hose Bottom Bucket...
  • Page 451 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Blade / travel hose (Important) The hydraulic hose (for blade/swing) should be replaced every two 1) Blade/swing hose routing years or 400 hours of operation, whichever is earlier. 2) Travel hose routing (rotary joint upper)
  • Page 452 U20-3, U25-3 WSM Hydraulic system (Service section) 3) Travel, swivel, swing and blade hose routing (rotary joint upper) High-pressure hose Unload valve Part No. Q’ty Swivel motor Location U-20-3 U-25 ← C/V~R/J Travel left forward RB411-6441Δ Blue (Two-speed) White ←...
  • Page 453 U20-3, U25-3 WSM Hydraulic system (Service section) [4] Pilot hose 1) List of pilot hoses Unload valve Front P/V (left) Front P/V (right) Blue Sky- Brown blue Yellow Pink Green Gray Back Back Control valve Bottom Left Bottom Bottom Travel...
  • Page 454 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Pilot hose routing Downword 3) Assembling procedure (1) Cord band (2) Cord band (3) Cord band 55311-4126Δ 55311-4126Δ 55311-4126Δ Clamp the travel lock hose, pilot Clamp at the taping (white) Clamp the hose and round bar hose and round bar guide portion of the hose.
  • Page 455 U20-3, U25-3 WSM Hydraulic system (Service section) i. Other hydraulic valve [1] Selector valve 1) Reassembling procedure: 1. Tightening torque of hydraulic adapter G1/4 : 24.5~29.4N⋅m (2.5~3.0kgf⋅m) G3/8 : 49.0~53.9N⋅m (5.0~5.5kgf⋅m) For the mounting direction and angle of the hydraulic adapter, refer to the figure to the left.
  • Page 456 U20-3, U25-3 WSM Hydraulic system (Service section) 2) Installing the selector valve (1) Tightening torque for installation of valve 48.1~55.9 N⋅m (4.9~5.7 kgf⋅m) (2) Tightening torque of adaptor G3/8: 49.0~53.9 N⋅m (5.0~5.5 kgf⋅m) G1/4: 24.5~29.4 N⋅m (2.5~3.0 kgf⋅m) Should not touch Part No.
  • Page 457 U20-3, U25-3 WSM Hydraulic system (Service section) [3] Accumulator (1) Tightening torque of accumulator hydraulic adaptor: G3/8: 49.0~53.9 N⋅m (5.0~5.5 kgf⋅m) Accumulator piping Part No. Part name Q'ty Remarks RB419-6281Δ Accumulator RB419-6385Δ Pipe joint (accumulator) 01133-61025 Bolt RP201-6181Δ Pipe joint (L, G3/8- G3/8) 1 RB419-6383Δ...
  • Page 458 U20-3, U25-3 WSM Hydraulic system (Service section) [4] Third line Part No. Part name Q'ty Remarks 11 RB419-9258Δ Hydraulic hose (1/2. third line) 12 RD418-9640Δ Valve assembly (third line) 13 RD418-9642Δ Bolt 14 RB419-9255Δ Plate (third line) 01123-60820 Bolt 16 RB419-9261Δ Hose (5/8-100, third line) 1 Fixed foot RB419-9262Δ...
  • Page 461 U20-3, U25-3 WSM Electrical system (Mechanism section) A.Components & harness layout Auto glow Slow blow fuse Engine harness Water temp. sensor (Gauge) Water temp. sensor (Auto glow) Fuel pump Battery Check relay(Er) Safety lock relay(B) Power outlet relay Meter panel...
  • Page 462 U20-3, U25-3 WSM Electrical system (Mechanism section) B.Function of main circuit a. Battery circuit Key SW 1 (AC) Stater motor Battery Alternator 1. Keep in mind that the battery voltage is applied through the above circuit all the time. 2. A 60A fuse is added close to the alternator, because otherwise part of the harness may get short-circuited due to the alternator's current generated while the engine is running.
  • Page 463 U20-3, U25-3 WSM Electrical system (Mechanism section) b. Safety Relay circuit (Automatic release function) 1. When the engine has started and the alternator has reached the specified rpm (N = 1 in the figure below), the auto release controller is activated to turn off by the auto release relay.
  • Page 464 U20-3, U25-3 WSM Electrical system (Mechanism section) c. Auto glow circuit Key SW Key on Key st Glow relay Glow plug Glow lamp Water tempt senser Auto glow controller Battery Fig 1 (1)Function 1. The glow controller receives a water temperature sensor signal or a key switch start position signal and makes the signal voltage (1) drop to the ground level.
  • Page 465 U20-3, U25-3 WSM Electrical system (Mechanism section) Fig 2. Function chart Key Switch Glow lamp Glow relay Sensor Open ° Water temp ( Fig 3. Timer curve Table 1. Timer function values ° Ω Water temp ( Thermistor resistance ( Pre-glow time (sec) 2.55...
  • Page 466 U20-3, U25-3 WSM Electrical system (Mechanism section) d. Fuel control circuit (1)Function FUEL FEED PUMP METER FUEL SENSOR METER WARNING LAMP HOLD FLOAT FUEL LEVEL COIL FUEL RESIDUAL SENSOR PULL-IN COIL Solenoid guide Stop lever Injection pump Engine stop solenoid...
  • Page 467 U20-3, U25-3 WSM Electrical system (Mechanism section) (2)Engine stop solenoid 1) Structure Specifications 1. Rated voltage : DC12V Suicide switch 2. Rated ampere filter Pull-in coil : 32A / DC12V Hold coil : 77A / DC12V at 20°C 3. Resistance...
  • Page 468 U20-3, U25-3 WSM Electrical system (Mechanism section) e. Engine oil pressure sensor circuit Check relay N.O. Charge N.c. lamp Meter Panel (Big) Oil pressure lamp Altrenal Check Regular lamp 1. Engine oil pressure sensor is N.C.(Normal close) type. 2. Check relay is N.O.(Normal open) type.
  • Page 469 U20-3, U25-3 WSM Electrical system (Mechanism section) f. Horn circuit (1)Structure (1) Diaphragm (5)Stop screw (2) Point (6)Stay (3) Horn coil (7)Air gap (4) Nut The horn consists of acoustic diaphragm, point, horn coil and other parts. It comes in spiral, flat and other types in construction.
  • Page 470 U20-3, U25-3 WSM Electrical system (Mechanism section) (3)Current flow (1) Battery (2) Horn switch (3) Horn relay (4) Diaphragm (5) Core (6) Coil (7) Moving bolt (8) Adjust nut (9) Moving plate Horn Relay Diode Switch For your information 1. Function of diode: Prevention of horn switch by absorbing the surge current.
  • Page 471 U20-3, U25-3 WSM Electrical system (Mechanism section) (4)Horn circuit (Horn SW is off position) Horn SW • When horn switch is off, current doesn’t flow through relay. So relay remains off condition and horn doesn’t sound. Horn Diode Horn SW •...
  • Page 472 U20-3, U25-3 WSM Electrical system (Mechanism section) g. Cab & Working lamp circuit Light SW Start Working Light Light Relay Heater relay Heater Main Harness Cabin Harness Heater SW Beacon SW Beacon Spare Spare Radio Wiper SW Wiper Battery Washer...
  • Page 473 U20-3, U25-3 WSM Electrical system (Mechanism section) h. Meter panel Circuit diagram TEMP FUEL Auto glow unit Regulator L-terminal 12p connector 6p connector Connection Connection Engine Pressure Lamp(+) (10) IG(+) Fuel unit (11) IG(+) Charge System lamp Empty Temp. unit...
  • Page 474 U20-3, U25-3 WSM Electrical system (Mechanism section) i. Heater circuit Heater SW Key SW Engine Stop Solenoid Heater Heater relay (1) Current flow 1.Turn the key switch to the ON position, and the battery current starts flowing to the heater relay, making the relay contact.
  • Page 475 U20-3, U25-3 WSM Electrical system (Mechanism section) j. Travel hi-speed control circuit R / G Travel hi- speed switch Troubleshooting: Travel hi-speed malfunction 1. Turn the key switch to the ON position to see if 12 V is applied to terminal 2 of the travel hi-speed switch.
  • Page 477 U20-3, U25-3 WSM Electrical system (Service section) V. Electrical system (Service section) A Wire harness installation ......................S-2 a Front ..........................S-3 b Engine ..........................S-4 c Swivel frame ........................S-5 d Around seet ........................S-7 B Troubleshooting ........................S-10 a Engine ........................... S-10 b Meter panel ........................
  • Page 479 U20-3, U25-3 WSM Electrical system (Service section) A Wire harness installation Precautions in clamping the electric wires 1. Do not allow the wire to touch things around the path. Do not touch the wire to a place where protective material is not used.
  • Page 480 U20-3, U25-3 WSM Electrical system (Service section) a Front V-S-3...
  • Page 481 U20-3, U25-3 WSM Electrical system (Service section) b Engine (1) Nut tightening torque for connecting cable to starter terminal 5.9~11.8N·m (0.6~1.2kgf·m) Grommet From front Water Glow plug temperature sensor Fuel pump Engine stop SOL Water temperature sensor V-S-4...
  • Page 482 U20-3, U25-3 WSM Electrical system (Service section) c Swivel frame V-S-5...
  • Page 483 U20-3, U25-3 WSM Electrical system (Service section) Around battery V-S-6...
  • Page 484 U20-3, U25-3 WSM Electrical system (Service section) d Around seat [1] Around seat Light relay Automatic release relay Automatic release Disconnection check relay stabilization relay Horn relay Cabin relay Starter lock relay Connect it to the light switch. Connect it to the key switch.
  • Page 485 U20-3, U25-3 WSM Electrical system (Service section) Lever lock switch Lever lock SOL Travel two-speed SOL To travel two-speed switch horn Cabin (heater) [2] Starter switch (1) Align the slot in the starter switch with the Projection Cover (upper right) (backside) projection on the cover (upper right).
  • Page 486 U20-3, U25-3 WSM Electrical system (Service section) [3] Around selector valve V-S-9...

  • Page 487: Troubleshooting

    U20-3, U25-3 WSM Electrical system (Service section) B Troubleshooting a Engine Trouble Check item Remedy Remarks 1. The starter does not run. (1) Check the slow-blow fuse (50A) and fuse (10A) for Check or replace. Fig.1, Fig.2 blowouts. (2) Check the battery terminal for looseness.
  • Page 488 U20-3, U25-3 WSM Electrical system (Service section) b Meter panel Trouble Check item Remedy Remarks 1. The glow lamp does not (1) Check by hand if the glow relay is running. Replace Fig.13 go on. (2) Check the meter-side coupler for disconnection.
  • Page 489 U20-3, U25-3 WSM Electrical system (Service section) Trouble Check item Remedy Remarks 5. The charge lamp does (1) Check the 60A fuse for blowouts. Replace not go off. (2) Check the alternator B terminal or coupler for Repair or replace disconnection.
  • Page 490 U20-3, U25-3 WSM Electrical system (Service section) c Others Trouble Check item Remedy Remarks 1. The machine does not (1) Check the fuse (5A) for blowouts. Replace run in spite of the (2) Check the lever lock solenoid coupler and switch Repair or replace Fig.33...

  • Page 491: Replacing Fuses

    U20-3, U25-3 WSM Electrical system (Service section) d Check instructions [1] Fuse 1 Check the continuity of the slow-blow fuse Fig.1 (50A) to see if the fuse is blown. (Fig.1) 2 Check the continuity of the fuse (10A) to Fig.2 see if the fuse is blown.
  • Page 492 U20-3, U25-3 WSM Electrical system (Service section) Fig.3 [2] Battery voltage 1. Start the engine. 2. Connect a circuit tester to the (+) terminal and (–) terminal of the battery and measure the voltage. (Fig.3) 10.5 V or higher: The battery is normal.
  • Page 493 U20-3, U25-3 WSM Electrical system (Service section) [4] Release controller Fig. 5 1. Disconnect the coupler CN310 from the controller. 2. Body-earth the controller coupler CN310-(6), set the key switch to the starting position and check if the engine starts. (Photo 1) Starting : The controller is faulty.
  • Page 494 U20-3, U25-3 WSM Electrical system (Service section) Fig.7 3. Continuity check (Fig.7) 2 Key switch: OFF 2 Check for continuity between the starter B terminal and battery (+) terminal. [6] Key switch 2 Disconnect the key switch and the key switch coupler CN14.
  • Page 495 U20-3, U25-3 WSM Electrical system (Service section) [8] Engine stop solenoid Fig.11 1. Measuring the voltage of the engine stop solenoid (Fig.11) 2 Disconnect the engine stop solenoid coupler CN36. 2 Measure the voltage between the coupler CN36-(1) or (2) and the body earth.
  • Page 496 U20-3, U25-3 WSM Electrical system (Service section) 3. Measuring the voltage of the glow plug Fig.15 (Fig.15) 2 Disconnect the glow plug LE terminal. 2 Key switch: ON 2 Measure the voltage between the LE terminal and body earth. * 12 V is indicated and then 0 V is indicated 10 seconds later.
  • Page 497 U20-3, U25-3 WSM Electrical system (Service section) 7. Continuity check Fig.19-1 2 Key switch: OFF 2 Disconnect the coupler. (1)Check for continuity between the battery ({) and glow relay coupler CN17-(4). (2)Check for continuity between the glow plug and glow relay coupler CN17-(3).
  • Page 498 U20-3, U25-3 WSM Electrical system (Service section) Fig.20 [10] Charge engine oil lamp 1. Check the alternator coupler and B terminal for disconnection. (Fig.20) 2. Check the oil switch coupler CN28-(1) for disconnection. (Fig.21) 3. Measuring the voltage of the oil switch coupler CN28-(1) (Fig.22)
  • Page 499 U20-3, U25-3 WSM Electrical system (Service section) 5. Measurement of engine oil pressure Fig.24 Measure the engine oil pressure. Idling 0.4MPa (4kgf / cm 0.6MPa (4kgf / cm * Oil switch actuating pressure Standard value:0.05 ± 0.01MPa (0.5 ± 0.1kg f / cm 6.
  • Page 500 U20-3, U25-3 WSM Electrical system (Service section) [11] Water temperature gauge Fig.26 1. Disconnect the water temperature gauge coupler.(Fig.26) 2 Key switch: ON 2 Measure the voltage of the water temperature gauge coupler CN313 (1). 12V: Normal Other than 12 V: Check for continuity.
  • Page 501 U20-3, U25-3 WSM Electrical system (Service section) [12]Fuel sensor Fig.29 1. Check the relay coupler CN23 of the fuel sensor for disconnection. (Fig.29) Fig.30 2. Measuring the voltage of the fuel sensor coupler (Fig.30) • Disconnect the coupler CN23. • Key switch: ON 12 V : Normal.
  • Page 502 U20-3, U25-3 WSM Electrical system (Service section) 5. Inspection of fuel sensor (Fig.32) Fig.32 • Remove the fuel sensor from the tank and inspect it. • Put the (+) test lead on the coupler CN23 (3) terminal. • Put the (–) test lead on the plated portion and measure the resistance.
  • Page 503 U20-3, U25-3 WSM Electrical system (Service section) 3. Check if a voltage is applied to the lever lock Fig.35 solenoid coupler and lever lock switch coupler. • Disconnect the coupler. • Key switch: ON (1) Measure the voltage between the solenoid valve coupler CN12-(1) and (2).
  • Page 504 U20-3, U25-3 WSM Electrical system (Service section) 6. Inspection of lever lock switch (Fig.38) Fig.38 Key switch: OFF Turn ON/OFF the lever lock switch by moving the unload lever of the right control lever and check if the pointer of the tester shakes.
  • Page 505 U20-3, U25-3 WSM Electrical system (Service section) [14]Horn Fig.41 1. Measuring the voltage of the horn terminal (Fig.14) • Key switch : ON • Horn switch: ON 12 V : Normal. Inspect the horn. Other than 12 V : Check for continuity.
  • Page 506 U20-3, U25-3 WSM Electrical system (Service section) [15]working light Fig.45 1. Measuring the voltage of the working light • Key switch : ON • Light switch : ON 12 V : Normal. Inspect the light. Other than 12 V: Check for continuity.
  • Page 508 KUBOTA Corporation CONSTRUCTION MACHINERY DIVISION 1-1-1 NAKAMIYA-OHIKE, HIRAKATA-CITY, OSAKA, JAPAN EDITOR: CONSTRUCTION MACHINERY MANUFACTURING DEPT. SERVICE SECTION HIRAKATA PLANT 1-1-1 NAKAMIYA-OHIKE, HIRAKATA-CITY, OSAKA, JAPAN PHONE :+81-72-840-1195 :+81-72-840-1195 KUBOTA Corporation Printed in Japan 0308.AK.e.05 Code No.97899-60740...

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