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Brake Assist System Testing

WARNING: This page is about a different car, the 2003 Pontiac Montana, 2003 Oldsmobile Silhouette, and 2003 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
  1. Were you sent here from Brake Symptom Table? If so, go to next step. If not, go to DIAGNOSTIC STARTING POINT - HYDRAULIC BRAKE  under TROUBLE SHOOTING.
  2. Inspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL MEASUREMENT & INSPECTION  under ADJUSTMENTS & INSPECTIONS. 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  under ADJUSTMENTS & INSPECTIONS. 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. 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 MEASUREMENT & INSPECTION  under ADJUSTMENTS & INSPECTIONS. 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  under SYSTEM TESTING. Is the vacuum reading within the acceptable limits? If so, go to next step. If not, see appropriate ENGINE MECHANICAL article in ENGINES.
  6. During the vacuum source inspection, did the power brake booster check valve operate properly? If so, go to step  8 . If not, go to next step.
  7. Replace the power brake booster check valve. See POWER BRAKE BOOSTER CHECK VALVE AND/OR HOSE REPLACEMENT  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, 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 power brake 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. See POWER BRAKE BOOSTER  and BRAKE PEDAL ASSEMBLY  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  13 .
  12. Replace the power brake booster. See POWER BRAKE BOOSTER  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  13. Install or connect any components that were removed or disconnected during diagnosis. Did you complete the operation? If so, system is okay. If system is not okay, go to step  2 .
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