Komatsu 830E Shop Manual page 386

CALIPER PISTON
Piston Assembly Removal
1. Position brake caliper so that return pin nut (1) is
in an upright position. (Refer to Figure 6-7).
2. Hold return pin (10) in place with a narrow bladed
screwdriver or hex key wrench and remove nut
(1).
3. Using a 0.25 in. (6.35 mm) diameter copper or
brass drift and a plastic mallet, gently tap on the
end of the pin to drive piston assembly from
housing. Carefully remove dust shield (12) from
groove of housing and from groove in piston.
4. Remove O-ring seal (7) and backup ring (16)
from the housing using a soft non-metallic round
edged tool.
5. Necessary functional inspections of piston return
mechanism can be made without disassembly of
piston assembly. Piston assembly may be disas-
sembled for detailed inspection, reassembled
and readjusted.
6. If piston assembly can be cleaned thoroughly
without disassembly, and if piston surface condi-
tion is acceptable for reuse, then piston assembly
can be functionally inspected for operation of the
return mechanism, and if satisfactory, returned to
service.
Inspection
1. Inspect piston surfaces for nicks, scratches or
rust.
2. Inspect housing bore for nicks, scratches or rust.
Minor nicks, scratches and rust can be removed
with fine emery cloth providing the following wear
limits are not exceeded:
•
Piston O.D. . . . . . . 2.621 in. (66.5 mm) min.
•
Housing Bore I.D. . 2.630 in. (66.8 mm) max.
3. Replace parts if worn beyond above limits.
Piston Assembly Installation
1. Lubricate pistons, seals, and housing bores with
clean C-3 hydraulic oil.
2. Install piston O-ring (7, Figure 6-7) into housing
seal groove and push to bottom of groove. (Con-
sidering opening to housing bore as top.)
3. Install backup ring (16) into top of housing seal
groove with concave or curved side against O-
ring.
J6-6
1. Brake Housing
2. Return Pin Washer
3. O-Ring
4. Return Pin Nut
When installing dust shields, avoid applying pres-
sure on shields over sharp edge of shield groove
surrounding piston cavities. Underside of shields
can be cut if care is not taken and cause failure of
shields in service.
DO NOT tighten nuts with hydraulic pressure
applied to piston or caliper assembly.
Rockwell Armature Speed Rear Disc Brakes
FIGURE 6-4. PISTON ASSEMBLY INSTALLATION
4. With brake housing lying on mounting face, gen-
tly push piston assembly (7, Figure 6-4) past pis-
ton seal assembly (5) until O-ring (3) and washer
(2) are seated in bottom of cavity.
5. Install new or reusable dust shields (6). Keep
these parts free of lubricant.
6. Position and support housing assembly on bench
with return pins up. Install return pin nuts with
washers (4) where required. Hold return pin from
turning with a narrow-bladed screwdriver or hex
key wrench, and tighten nuts to 135 ±15 in.lbs.
(15.3 ±1.7 N.m) torque.
7. Place brake housing assembly on arbor press,
press piston assembly into cavity to fully retracted
position as shown in Figure 6-5.
5. Piston Seal Assembly
6. Dust Shield
7. Piston Assembly
J06020