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®
®
Bendix
AD-4
Air Dryer
SUPPLY
PORT
THERMOSTAT
TERMINAL
EXTENDED PURGE AD-4
FIGURE 1 - AD-4
AIR DRYER MODELS
DESCRIPTION
The function of the AD-4
air system contaminants in solid, liquid and vapor form be-
fore they enter the brake system. It provides clean, dry air
to the components of the brake system which increases
the life of the system and reduces maintenance costs. Daily
manual draining of the reservoirs is eliminated.
The AD-4
air dryer consists of a desiccant cartridge and a
die cast aluminum end cover secured to a cylindrical steel
outer shell with eight cap screws and nuts. The end cover
contains a check valve assembly, a safety valve, purge valve
mechanism, a cast-in heater element with a replaceable
thermostat assembly and three threaded air connections.
PURGE
EXHAUST
AIR DRYER
air dryer is to collect and remove
UPPER
BRACKET
LOWER
BRACKET
CONTROL
PORT
DELIVERY PORT
The three air connections are identified with embossed
numbers and lettering. The identification and function of each
is as follows:
Port l.D.
CON 4 ................ Control Port
SUP 11 .............. Supply Port (air in).
DEL 2 ................ Delivery Port (air out).
A cast-in heater element and replaceable thermostat with
an external terminal are provided.
The voltage and wattage requirements of the heater and
thermostat are shown with embossed numbers and letters
in the recess adjacent to the control port marked "CON. "
PURGE
EXHAUST
STANDARD AD-4
AIR DRYER
Function/Connection
(from unloader port on governor).
UPPER
BRACKET
LOWER
BRACKET
SUPPLY
PORT
1

Summary of Contents

  • Page 1

    ® ® ™ Bendix AD-4 Air Dryer UPPER UPPER BRACKET BRACKET LOWER LOWER BRACKET BRACKET SUPPLY PORT CONTROL PORT SUPPLY PORT PURGE DELIVERY PORT PURGE EXHAUST THERMOSTAT EXHAUST TERMINAL ™ ™ EXTENDED PURGE AD-4 AIR DRYER STANDARD AD-4 AIR DRYER FIGURE 1 - AD-4 ™...

  • Page 2

    CHECK VALVE ORIFICE PURGE VOLUME DESICCANT CARTRIDGE DESICCANT OIL SEPARATOR CHECK VALVE DELIVERY PORT HEATER EXHAUST PORT CONTROL COMPRESSOR GOVERNOR PURGE VALVE SUPPLY RESERVOIR ™ FIGURE 2 - AD-4 AIR DRYER CHARGE CYCLE OPERATION OF THE AD-4 ™ AIR DRYER The AD-4 ™...

  • Page 3

    CHECK VALVE ORIFICE PURGE VOLUME DESICCANT CARTRIDGE DESICCANT OIL SEPARATOR CHECK VALVE DELIVERY PORT EXHAUST HEATER PORT COMPRESSOR CONTROL GOVERNOR PURGE VALVE SUPPLY RESERVOIR ™ FIGURE 3 - AD-4 AIR DRYER PURGE CYCLE line connecting the governor unloader port to the AD-4 ™...

  • Page 4

    CHECK PURGE VALVE ORIFICE PURGE VOLUME DESICCANT CARTRIDGE DESICCANT CHECK VALVE PERFORATED PLATE ASSEMBLY OIL SEPARATOR SEALING RING WASHER SEALING RING SEALING RING SEALING RING END COVER SUPPLY PORT SPECIAL SPRING WASHER PURGE PISTON DELIVERY O-RING HEX HEAD PORT EXHAUST SCREW EXHAUST PURGE...

  • Page 5

    2. Check mounting bolts for tightness. Retorque to 270- 6. Check the operation of the end cover heater and 385 inch pounds. thermostat assembly during cold weather operation as follows: 3. Perform the Operation & Leakage Tests listed in this publication.

  • Page 6

    When rebuilding or replacing components of the air dryer removed. Where circumstances require that the use only genuine Bendix parts. For ease in servicing the engine be in operation, EXTREME CAUTION should ™...

  • Page 7

    MOUNTING STRAP LOCKWASHER CAP SCREW 5/16” X 4-1/2” SEALING RING BRACKET MOUNTING STRAP LOCKWASHER CAP SCREW SEALING PLATE 5/16” X 4-1/2” BRACKET MOUNTING BRACKET HOOK (4) DESICCANT CARTRIDGE (8) LOCK NUT CAP SCREW & LOCKWASHER (8) SPECIAL WASHER SEALING RING AIR DRYER HOUSING SEALING RING...

  • Page 8

    Never remove a component or plug unless you are certain all system pressure has been depleted. FIGURE 7 - LOWER BRACKET INSTALLATION 8. Use only genuine Bendix ® replacement parts, components and kits. Replacement hardware, tubing, hose, fittings, etc.

  • Page 9

    the end cover. Remove and discard the three sealing ASSEMBLY rings. One sealing ring is located in the groove on the Prior to assembly, coat all o-rings, o-ring grooves, and bores sealing plate and the other two are in grooves in the end with a generous amount of barium base lubricant.

  • Page 10

    3/8" bolts require replacement, insure that the 5. Cut uninsulated thermostat wire at Point B, remove and replacement bolts are grade 5 minimum and the same discard thermostat and terminal assembly (1). length as the original bolts. Use of inferior bolts can 6.

  • Page 11

    17 CFM that an authorized Bendix parts outlet or Bendix marketing representative be contacted for assistance. The preceding portion of this manual deals with “in-service”...

  • Page 12

    Bendix parts outlet. motion. The AD-4 ™ air dryer must not be exposed to 3.

  • Page 13

    AD-4 ™ air dryer will not cycle excessively. (A) Total air system leakage (See Bendix publication BW-5057 “Air Brake Handbook”). (B) Compressor unloader mechanism. (C) Governor. (D) Drain cock and safety valve in first (supply) reservoir.

  • Page 14

    ™ AD-4 AIR DRYER TROUBLESHOOTING CHART REMEDY SYMPTOMS CAUSE 1. Dryer is constantly A. Excessive system A. If leakage IS SHOWN on gauges test for “cycling” or purging. leakage. excessive service brake system leakage. Dryer purges frequently IMPORTANT: Note whether Allowable leakage: (every 4 minutes or less air pressure loss is shown...

  • Page 15

    ™ AD-4 AIR DRYER TROUBLESHOOTING CHART (Continued) REMEDY SYMPTOMS CAUSE 1. Test fittings, hoses, lines and connections. Apply soap solution to detect excessive leakage. Tighten or replace as needed then repeat the air dryer charge-purge cycle and observe the gauge installed in the supply reservoir.

  • Page 16

    Make certain Holset ECON is not used with the drop-in version of the air dryer, if so, remove and retest. When installing a Bendix Drop-In air dryer in a system equipped with a Holset E or QE compressor, remove the Holset ECON valve along with its feed back and governor control line.

  • Page 17

    Consult your local authorized Bendix parts outlet frequent stops, excessive leakage from fittings, or sales representative for additional information.

  • Page 18

    90 degree fitting, it may be changed to a straight or 45 degree fitting. For more information on how to help prevent discharge line freeze-ups, see Bendix Bulletins TCH-08-21 and TCH-08-22. Shorter discharge line lengths or insulation may be required in cold climates.

  • Page 19

    ™ AD-4 AIR DRYER TROUBLESHOOTING CHART (Continued) REMEDY SYMPTOMS CAUSE H. If vehicle uses Holset compressor, inspect H. Air by-passes desiccant feedback check valve for proper installation and cartridge assembly. operation. When replacing the desiccant cartridge, make sure desiccant cartridge assembly is properly installed and sealing rings are in place on mounting surface of desiccant cartridge.

  • Page 20

    ™ AD-4 AIR DRYER TROUBLESHOOTING CHART (Continued) REMEDY SYMPTOMS CAUSE F. Governor malfunction. F. Test governor operation and/or inspect the Missing or restricted control line leading from the governor UNL governor control line (unloader) port to the air dryer control port. installation.

  • Page 21

    ™ AD-4 AIR DRYER TROUBLESHOOTING CHART (Continued) REMEDY SYMPTOMS CAUSE A. This symptom is almost A. See Causes and Remedies for Symptoms 1, 2, 8. Desiccant material being always accompanied by 3, 4 and 5. expelled from air dryer one or more of purge valve exhaust Symptoms 1, 2, 3, 4 and (may look like whitish...

  • Page 22

    250,000 miles. covered under warranty. Note: To help prevent discharge line freeze-ups, shorter discharge line lengths or insulation may be required in cold climates. (See Bendix Bulletins TCH-08-21 and TCH-08-22, included in Appendix B, for more information.) 5 For certain vehicles/applications, where turbo-charged inlet air is used, a smaller size...

  • Page 23

    The troubleshooting procedure presented on the following pages has been excerpted from a laminated card entitled: Troubleshooting Charging and Air Supply Systems. The complete card can be obtained from authorized Bendix parts outlets under literature number BW1779. It is presented here because of the air dryers connection to the supply air system and for convenience.

  • Page 24

    BW1450 © 2004 Bendix Commercial Vehicle Systems LLC All rights reserved. 10/2004 Printed in U.S.A.

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