Chrysler Full-Size Trucks 1989-1996 Repair Guide

Combination Valve

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TESTING



Metering Valve

The metering valve can be checked visually and with the aid of a helper.

  1. While the helper applies and releases the brakes, observe the metering valve stem.
  2.  
  3. If the valve is operating correctly, the stem will extend slightly when the brakes are applied and retract when they are released.
  4.  
  5. If the valve is found faulty, replace the entire combination valve as an assembly.
  6.  

Pressure Differential Switch

  1. Have a helper sit in the driver's seat to apply the brake pedal and observe the red brake warning light.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Connect a bleed hose to a rear wheel cylinder and immerse the other end in a container partially filled with fluid.
  6.  
  7. Have the helper press and hold the brake pedal to the floor and watch the warning light.
    1. If the warning light illuminates, the switch os operating normally.
    2.  
    3. If the light fails to illuminate, check the circuit fuse bulb and wiring. Repair as necessary and repeat this test.
    4.  

  8.  
  9. If after making necessary repairs, the warning light still does not come on, check the brake light and parking brake switches and wiring with a test lamp to verify basic operation. Repair or replace parts as necessary and test the differential pressure switch operation again.
  10.  
  11. If the warning light still fails to illuminate, the switch is faulty. Replace the combination valve assembly, bleed the brake system and verify proper switch and valve operation.
  12.  
  13. Lower the vehicle.
  14.  

REMOVAL & INSTALLATION



The combination valve and mounting bracket are serviced as an assembly. They are permanently attached and should not be separated.

Pick-Ups
  1. Disconnect the ground wire and harness wire from the combination valve switch and RWAL valve.
  2.  
  3. Disconnect the lines to the front and rear brakes from the RWAL and combination valves.
  4.  
  5. Remove the brake lines connecting the master cylinder to the combination valve.
  6.  
  7. Remove the nuts attaching the master cylinder and combination valve bracket to booster studs.
  8.  
  9. Remove the master cylinder.
  10.  
  11. Remove the combination valve, valve bracket and RWAL valve as an assembly.
  12.  
  13. Remove the brake line connecting the combination valve to the RWAL valve.
  14.  
  15. Remove the bolt attaching the RWAL valve to the combination valve and bracket assembly. Then, separate the RWAL valve from the bracket.
  16.  

To install:
  1. Install the RWAL valve on the combination bracket. DO not tighten the RWAL valve bolt completely at this time.
  2.  
  3. Install the short brake line that connects the RWAL valve to the combination valve. Tighten the line fittings to 12-17 ft. lbs. (16-23 Nm).
  4.  
  5. Tighten the RWAL valve attaching bolt to 17-25 ft. lbs. (23-34 Nm).
  6.  
  7. Install the master cylinder on the booster mounting studs.
  8.  
  9. Attach the anti-lock harness ground wire to the combination valve bracket.
  10.  
  11. Install the combination valve bracket on the booster mounting studs and against the master cylinder.
  12.  
  13. Loosely install the nuts that retain the master cylinder and combination valve on the booster studs.
  14.  
  15. Install and connect all remaining brake lines. Tighten the fittings to 12-17 ft. lbs (16-23 Nm).
  16.  
  17. Connect the harness wires to the RWAL valve and the combination valve switch.
  18.  
  19. Fill and bleed the brake system according to the proper procedure.
  20.  

Dakota Models

  1. Disconnect and remove the battery for easier access to the valves and lines.
  2.  
  3. Disconnect the rear brake line at the rear anti-lock valve.
  4.  
  5. Disconnect the brake line from the front anti-lock valve at the combination valve.
  6.  
  7. Disconnect the harness wires at the rear anti-lock and combination valves.
  8.  
  9. Disconnect the ground wire at the combination valve bracket.
  10.  
  11. Remove the nuts attaching the combination valve bracket to the brake booster studs.
  12.  
  13. Disconnect the brake lines connecting the rear anti-lock valve to the master cylinder.
  14.  
  15. Slide the combination valve bracket off the brake booster studs.
  16.  
  17. Remove the rear anti-lock valve, combination valve and bracket, and attached brake lines as an assembly.
  18.  
  19. Remove the brake line connecting the rear anti-lock valve to the combination valve.
  20.  
  21. Remove the bolt attaching the rear anti-lock valve to the combination valve bracket. Then, separate the rear anti-lock valve from the bracket.
  22.  
  23. If the combination valve is to be replaced, remove the connecting brake lines from the valve.
  24.  

To install:
  1. If a new combination valve is being installed, transfer the brake lines that connect the valve to the master cylinder. Leave the fittings loose. Do not fully tighten them at this time.
  2.  
  3. Install the rear anti-lock valve on the combination valve bracket. Tighten the attaching bolt securely.
  4.  
  5. Install the brake line that connects the front anti-lock valve to the combination valve. Do not fully tighten the fitting at this time.
  6.  
  7. Install the valve and bracket assembly on the brake booster mounting studs. Tighten the mounting nuts to 17-21 ft. lbs. (23-28 Nm).
  8.  
  9. Attach the ground wire to the combination valve bracket. Make sure it is securely attached, and that the connection is clean.
  10.  
  11. Connect the brake lines to the master cylinder, rear anti-lock valve and combination valve. Tighten the fittings at the rear anti-lock valve to 10-15 ft. lbs. (13-20 Nm). Tighten all other line fittings to 12-17 ft. lbs. (16-23 Nm).
  12.  
  13. Connect the wire harnesses to the rear anti-lock and combination valves.
  14.  
  15. Install and connect the battery.
  16.  
  17. Fill and bleed the brake system according to the proper procedure.
  18.  

 
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