Aug 192015
 

Have replaced the brake and steering hydroboost because it was leaking.
Did the bleeding procedure but each time I start the truck now the brakes depress themselves. I am stumped do you have some one with experience with the hydroboost on large trucks.

  One Response to “1996 GMC C3500”

  1. Slow or incomplete pedal return:

    Step 1) Run pump at fast idle.

    Step 2) Pull the brake pedal rearward with approximately 10 lbs. force and release. Measure the distance to the floorboard.

    Step 3) Make 100-lb. brake application. Release brake pedal and measure distance to floorboard. The brake pedal should return to its normal position (step 2). If measurements are the same, go to step 5.

    Step 4) If the brake pedal does not return properly, check the pedal to be sure it is operating freely. Correct any sticking or binding as necessary.

    Step 5) If brakes are self applying and pedal is free, check for obstruction in the return line or a kinked connection between hydo-boost and pump reservoir. If obstruction or kink is found, go to step 6, otherwise go to step 7.

    Step 6) Remove obstruction or replace line as required. If condition remains, check for a damaged reaction end. If damaged the hydo-boost should be replaced or repaired.

    Step 7) If brake pedal is free of any binding conditions and return line is free of obstructions, remove the master cylinder cover.

    Step 8) Observe the brake fluid in the reservoir while rapidly depressing the brake pedal one inch.

    Step 9) Fluid surface should have some movement or spout in the forward reservoir section. Minor spouting may occur in the rearward reservoir. If no movement or spouting of fluid occurs in forward reservoir, the hydro-boost unit is defective and must be replaced or repaired.

    Excessive pedal effort – brake pedal chatter – pulsation and/or leaks:

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