Chrysler Full-Size Trucks 1967-1988 Repair Guide

Hydraulic Valves

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See Figure 1

Models with front and rear drum brakes are equipped with a brake warning light switch mounted in a housing on the frame rail. The front and rear brake lines are connected to the housing and a moving valve inside the housing reacts to changes in hydraulic pressure, warning the driver of excessively low pressure in either or both systems.



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Fig. Fig. 1: Common proportioning valve assembly

Models with front disc brakes incorporate the safety switch with either a metering valve or combination metering/proportioning valve

REMOVAL & INSTALLATION



See Figures 2, 3, 4 and 5

  1. Raise and support the front end on jackstands.
  2.  
  3. Remove the splash shield.
  4.  
  5. Disconnect the wiring at the warning light switch.
  6.  
  7. Disconnect the brake lines at the valve.
  8.  
  9. Unbolt and remove the valve from the frame.
  10.  

To install:
  1. Install the valve, then connect the lines and wiring.
  2.  
  3. Properly bleed the brake system.
  4.  
  5. Install the splash shield.
  6.  
  7. Remove the jackstands and carefully lower the vehicle.
  8.  



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Fig. Fig. 2: Brake warning switch/metering valve set up for W-series through 1974



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Fig. Fig. 3: Brake warning switch/metering valve for D-series models 1967-1974



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Fig. Fig. 4: 1975-76 brake warning/metering valve



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Fig. Fig. 5: Brake warning switch/metering valve for 1977-88 models

CENTERING THE PROPORTIONING VALVE



After the brake system has been opened for any reason, the warning light will remain ON until the proportioning valve is centralized. All proportioning valves are self-centering after the brakes are properly bled.

  1. Raise and support the front end on jackstands.
  2.  
  3. Remove the splash shield.
  4.  
  5. Turn the ignition switch to ON .
  6.  
  7. Crack a front bleeder screw, have an assistant apply the brakes to produce a front failure condition. The warning light will come on and stay on.
  8.  
  9. Bleed the rear brakes, then the front brakes.
  10.  
  11. After bleeding both front and rear brakes apply moderate force to the brake pedal. This will hydraulically recenter the proportioning valve and turn off the warning light.
  12.  
  13. Refill the master cylinder.
  14.  
  15. Check the brake pedal for any air left in the system, if needed repeat the bleeding procedure until a good pedal is obtained.
  16.  
  17. Lower the vehicle and test drive.
  18.  

 
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