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Vacuum Assist

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Were you sent here from DIAGNOSTIC STARTING POINT - HYDRAULIC BRAKES? If so, go to next step. If not, see DIAGNOSTIC STARTING POINT - HYDRAULIC BRAKES  .
  2. Inspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL  . Is the brake pedal travel distance within the acceptable limits? If so, go to step  5 . If not, go to next step.
  3. Inspect for worn, missing, misaligned, bent or damaged brake pedal system components.
    • For the brake pedal pushrod component inspection, see BRAKE PEDAL PUSHROD INSPECTION  .
    • Inspect the brake pedal bushings for excessive wear and/or damage and inspect the brake pedal for a misaligned, bent and/or damaged condition.
    Replace the brake pedal system components that are worn, missing, misaligned, bent or damaged, refer to the following procedures as necessary. Did you find and replace any worn, missing, misaligned, bent or damaged brake pedal system components? If so, go to next step. If not, go to step  5 .
  4. Reinspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL  . Is the brake pedal travel distance within the acceptable limits? If so, go to step  8 . If not, go to next step.
  5. Check the engine vacuum source that supplies vacuum to the power brake booster. See BRAKE SYSTEM VACUUM SOURCE TEST  . Is the vacuum reading within the acceptable limits? If so, go to next step. If not, investigate vacuum leak. See Engine Mechanical.
  6. During the vacuum source inspection, did the vacuum booster check valve operate properly? If so, go to next step  8 . If not, go to next step.
  7. Replace the vacuum booster check valve. See POWER BRAKE BOOSTER CHECK VALVE  . After repairs are complete, go to next step.
  8. Pump the brake pedal several times until the brake pedal becomes hard. Maintain moderate foot pressure on the brake pedal and start the engine. Observe pedal operation. Did the brake pedal drop slightly, then remain firm after the engine was started? If so, go to next step. If not, go to step  12 .
  9. Release the brake pedal. Turn the ignition OFF, then wait 15 seconds. Pump the brake pedal 2 times to check for vacuum booster available vacuum reserve. Observe pedal effort. (If operating properly, the power brake booster should maintain assist for at least 2 pedal applications.) Did the brake pedal effort increase significantly? If so, go to step  12 . If not, go to next step.
  10. Inspect the brake pedal pushrod and the brake pedal for misalignment, a bent condition and/or damage. Is the brake pedal pushrod and/or the brake pedal misaligned, bent or damaged? If so, go to next step. If not, go to step  13 .
  11. Replace the brake pedal pushrod and/or the brake pedal, as necessary. Refer to the following procedure(s). After repairs are complete, go to step  13 .
  12. Replace the power brake booster. See POWER BRAKE BOOSTER  . After repairs are complete, go to next step.
  13. Install or connect any components that were removed or disconnected during diagnosis. If condition is still present, go to step  2 . If condition is corrected, system is okay.
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