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Home >> Chevrolet >> 2002 >> Astro Van Passenger, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 57 (Disc Brakes) >> Trouble Shooting >> General Diagnosis (Brake Assist) >> Brake Assist System Diagnosis

Brake Assist System Diagnosis

WARNING: This page is about a different car, the 2003 GMC Safari and 2003 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Were you sent here from a Brake Symptom List? If so, go to next step. If not, go to GENERAL DIAGNOSIS (HYDRAULIC BRAKES) .
  2. Is the symptom related to brake system noise? If not, go to next step. If so, go to step  4.
  3. Is the symptom related to the brake system self-applying when the steering wheel is being turned? If so, go to step  14. If not, go to step  9.
  4. Check the hydraulic assist system operation for the presence of abnormal noise. Did the noise inspection indicate a concern with power steering system drive belt? If so, go to next step. If not, go to step  6.
  5. Replace power steering system drive belt. After completing repair, go to next step.
  6. Did the noise inspection indicate a possible restriction in the hydraulic brake booster power steering system return hose? If ye, go to next step. If not, go to step  8.
  7. Replace restricted hydraulic brake booster power steering return hose. See appropriate STEERING article. After completing repair, go to next step.
  8. During the noise inspection, did the hydraulic brake booster produce abnormal noises? If so, go to step  14. If not, go to next step.
  9. Inspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL  under ADJUSTMENTS. Is brake pedal travel distance within the acceptable limits? If so, go to step  12. If not, go to next step.
    • Inspect for worn, missing, misaligned, bent or damaged brake pedal system components.
      1. Inspect brake pedal pushrod components.
      2. Inspect brake pedal bushings for excessive wear and/or damage and inspect the brake pedal for a misaligned, bent and/or damaged condition.
    • Replace brake pedal system components that are worn, missing, misaligned, bent or damaged, refer to the following procedures as necessary.
      1. See BRAKE PEDAL  under REMOVAL & INSTALLATION.
      2. See BRAKE BOOSTER  under REMOVAL & INSTALLATION.
    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  12.
  11. Reinspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL  under ADJUSTMENTS. Is the brake pedal travel distance within the acceptable limits? If so, go to step  14. If not, go to next step.
  12. Inspect power steering drive belt for conditions which could cause slipping. Replace power steering drive belt if necessary. See appropriate ENGINE article. Check the power steering system fluid level and adjust level if necessary. See appropriate STEERING article. Go to next step.
  13. With ignition off, depress brake pedal 4 times or until the effort required to apply the pedal increases significantly. Maintain moderate foot pressure on the brake pedal and start engine. Observe pedal operation. Did the brake pedal fall slightly, then hold after the engine was started? If so, go to step  16. If not, go to next step.
  14. Inspect power steering system pressure supplying the hydro-boost unit. See appropriate STEERING article. Replace power steering components as indicated by the results of the pressure analysis. Did you find and correct a condition? If so, go to next step. If not, go to step  19.
  15. With ignition off, depress brake pedal 4 times or until the effort required to apply the pedal increases significantly. Maintain moderate foot pressure on the brake pedal and start the engine. Observe pedal operation. Did brake pedal fall slightly, then hold after the engine was started? If so, go to next step. If not, go to step  19.
  16. Release brake pedal. Allow engine to continue to idle in order to pressurize the system. Turn ignition off. Wait 90 seconds, then depress the brake pedal 2 times to check for hydraulic brake booster immediate reserve. Observe pedal effort. Did the brake pedal apply effort significantly increase when the brake pedal was applied the second time? If so, go to step  19. If not, go to next step.
  17. Release brake pedal. Start engine to pressurize the system. Turn ignition off. Wait one hour, then depress the brake pedal 4 times to check for hydraulic brake booster accumulator reserve leak down. Observe pedal effort. Did the brake pedal apply effort significantly increase when the brake pedal was applied the fourth time? If so, go to next step. If not, go to step  20.
  18. Replace hydraulic brake booster accumulator assembly. See BRAKE BOOSTER ACCUMULATOR  under REMOVAL & INSTALLATION. After completing repair, go to step  20.
  19. Replace hydraulic brake booster assembly. See BRAKE BOOSTER  under REMOVAL & INSTALLATION. After completing repair, go to next step.
  20. Install or connect any components that were removed or disconnected during diagnosis. Return to Brake Symptom List that sent you to this test.
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