Avalanche, Sierra, Silverado, C&K Series, 1999-2005

Manual Bleeding

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To bleed the brakes on a vehicle equipped with ABS, please refer to the ABS bleeding procedure in this section.

The brake system must be bled when any brake line is disconnected or there is air in the system.


NOTE
Never bleed a wheel cylinder when a drum is removed.

  1. Clean the master cylinder of excess dirt and remove the cylinder cover and the diaphragm.
  2.  
  3. Fill the master cylinder to the proper level. Check the fluid level periodically during the bleeding process and replenish it as necessary. Do not allow the master cylinder to run dry, or you will have to start over.
  4.  
  5. Before opening any of the bleeder screws, you may want to give each one a shot of penetrating solvent. This reduces the possibility of breakage when they are unscrewed.

    Click image to see an enlarged view

    Fig. Connect one end of a clear plastic tube to the bleeder screw and submerge the other end in clean brake fluid



    Click image to see an enlarged view

    Fig. Have an assistant pump, then hold in the brake pedal, while you bleed each wheel

  6.  
  7. Attach a length of vinyl hose to the bleeder screw of the brake to be bled. Insert the other end of the hose into a clear jar half full of clean brake fluid, so that the end of the hose is beneath the level of fluid. The correct sequence for bleeding is to work from the brake farthest from the master cylinder to the one closest; right rear, left rear, right front, left front.
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  9. Depress and release the brake pedal three or four times to exhaust any residual vacuum.
  10.  
  11. Have an assistant push down on the brake pedal and hold it down. Open the bleeder valve slightly. As the pedal reaches the end of its travel, close the bleeder screw and release the brake pedal. Repeat this process until no air bubbles are visible in the expelled fluid.
    NOTE
    Make sure your assistant presses the brake pedal to the floor slowly. Pressing too fast will cause air bubbles to form in the fluid.

  12.  
  13. Repeat this procedure at each of the brakes. Remember to check the master cylinder level occasionally. Use only fresh fluid to refill the master cylinder, not the stuff bled from the system.
  14.  
  15. When the bleeding process is complete, refill the master cylinder, install its cover and diaphragm, and discard the fluid bled from the brake system.
  16.  


CAUTION
The following procedures apply to the BASE BRAKING SYSTEM ONLY. For bleeding Anti-Lock Brakes refer to the ANTI-LOCK BRAKE SYSTEM (ABS) Section.


WARNING
When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

  1. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
  2.  
  3. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
  4.  
  5. If you have performed a brake master cylinder bench bleeding on this vehicle, or if you disconnected the brake pipes from the master cylinder, you must perform the following steps:

    Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary add Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal.
     
    With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder.
     
    Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder.
     
    Reconnect the brake pipe to the master cylinder port and tighten securely.
     
    Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
     
    Loosen the same brake pipe to purge air from the open port of the master cylinder.
     
    Tighten the brake pipe, then have the assistant slowly release the brake pedal.
     
    Wait 15 seconds, then repeat steps until all air is purged from the same port of the master cylinder.
     
    With the front brake pipe installed securely to the master cylinder - after all air has been purged from the front port of the master cylinder - loosen and separate the rear brake pipe from the master cylinder, then repeat steps.
     
    After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.
     

  6.  
  7. Fill the brake master cylinder reservoir with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
  8.  
  9. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
  10.  
  11. Install a transparent hose over the end of the bleeder valve.
  12.  
  13. Submerge the open end of the transparent hose into a transparent container partially filled with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
  14.  
  15. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
  16.  
  17. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
  18.  
  19. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
  20.  
  21. Wait 15 seconds, then repeat steps 8-10 until all air is purged from the same wheel hydraulic circuit.
  22.  
  23. With the right rear wheel hydraulic circuit bleeder valve tightened securely - after all air has been purged from the right rear hydraulic circuit - install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
  24.  
  25. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
  26.  
  27. With the left rear wheel hydraulic circuit bleeder valve tightened securely - after all air has been purged from the left rear hydraulic circuit - install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
  28.  
  29. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
  30.  
  31. With the right front wheel hydraulic circuit bleeder valve tightened securely - after all air has been purged from the right front hydraulic circuit - install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
  32.  
  33. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
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  35. After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of the 4 wheel hydraulic circuit bleeder valves are properly tightened.
  36.  
  37. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11-, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
  38.  
  39. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
  40.  
  41. If the brake pedal feels spongy, repeat the bleeding procedure again. If the brake pedal still feels spongy after repeating the bleeding procedure, perform the following steps:

    Inspect the brake system for external leaks.
     
    Pressure bleed the hydraulic brake system in order to purge any air that may still be trapped in the system.
     

  42.  
  43. Turn the ignition key ON , with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
    CAUTION
    If the brake system warning lamp remains illuminated, DO NOT drive the vehicle until it is diagnosed and repaired.

  44.  

 
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