GM Full-Size Trucks 1988-1998 Repair Information

Combination Valve

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This valve is used on all models with disc brakes. The valve itself is a combination of:

  1. The metering valve, which will not allow the front disc brakes to engage until the rear brakes contact the drum.
  2.  
  3. The failure warning switch, which notifies the driver if one of the systems has a leak.
  4.  
  5. The proportioner which limits rear brake pressure and delays rear wheel skid.
  6.  

REMOVAL & INSTALLATION



R/V Series

See Figure 1

  1. Disconnect the hydraulic lines and plug them to prevent dirt from entering the system.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: Combination valve mounting-R/V Series

  1. Disconnect the warning switch harness.
  2.  
  3. Unfasten the retaining bolts and remove the valve.
  4.  
  5. Install the valve and tighten the retainers to 150 inch lbs. (17 Nm).
  6.  
  7. Bleed the brake system.
  8.  

C/K Series

MANUAL BRAKES

See Figure 2

  1. Disconnect the brake lines at the valve. Plug or cap the lines and ports.
  2.  
  3. Unplug the switch wiring connector.
  4.  
  5. Remove the valve-to-bracket bolts.
  6.  

To install:
  1. Install the valve. Tighten the bolts to 20 ft. lbs. (27 Nm).
  2.  
  3. Bleed the system.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: Combination valve-C/K Series

POWER BRAKES
  1. Disconnect the brake lines at the switch. Plug or cap the lines and ports.
  2.  
  3. Unplug the warning switch wiring connector.
  4.  
  5. Remove the anti-lock brake system control module from the bracket. See the procedure later in this section.
  6.  
  7. Remove the bolts attaching the ABS isolation/dump valve to the bracket. See the procedure later in this section.
  8.  
  9. Remove the nuts that attach the master cylinder and bracket to the booster.