Brake Assist System Diagnosis

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.

If sent here from a BRAKE SYMPTOM list, go to step 2 . If you were not sent here from a brake symptom list, see DIAGNOSTIC STARTING POINT (HYDRAULIC BRAKES) under TROUBLE SHOOTING.
Inspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL MEASUREMENT & INSPECTION under ADJUSTMENTS & INSPECTION. If the brake pedal travel distance is within the acceptable limits, go to step 5 . If the brake travel distance is not within the acceptable limits, go to step 3 .
- Inspect for worn, missing, misaligned, bent or damaged brake pedal system components.
  1. See BRAKE PEDAL PUSHROD INSPECTION under ADJUSTMENTS & INSPECTION.
  2. 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.
  1. See BRAKE PEDAL ASSEMBLY under REMOVAL & INSTALLATION.
  2. See POWER BRAKE BOOSTER under REMOVAL & INSTALLATION.
If any worn, missing, misaligned, bent or damaged brake pedal system components were found, go to step 4 . If any worn, missing, misaligned, bent or damaged brake pedal system components were not found, go to step 5 .
Inspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL MEASUREMENT & INSPECTION under ADJUSTMENTS & INSPECTION. If the brake pedal travel distance is within the acceptable limits, go to step 8 . If the brake pedal travel distance is not within the acceptable limits, go to step 5 .
Check the engine vacuum source that supplies vacuum to the vacuum brake booster. See BRAKE VACUUM TEST . If the vacuum reading is within the acceptable limits, go to step 6 . If the vacuum reading is not within the acceptable limits, see appropriate ENGINE MECHANICAL article in ENGINES.
During the vacuum source inspection, if the vacuum booster check valve operates properly, go to step 8 . If the vacuum booster check valve does not operate properly, go to step 7 .
Replace the vacuum booster check valve. If the replacement is completed, go to step 8 .
Pump the brake pedal several times until the brake pedal effort increases significantly. Maintain moderate foot pressure on the brake pedal and start the engine. Observe pedal operation. If the brake pedal dropped slightly, then remained firm after the engine was started, go to step 9 . If the brake pedal did not drop slightly and did not remain firm after the engine was started, go to step 12 .
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 vacuum brake booster should maintain assist for at least 2 pedal applications. If the brake pedal effort increased significantly, go to step 12 . If the brake pedal effort did not increase significantly, go to step 10 .
Inspect the brake pedal pushrod and the brake pedal for misalignment, a bent condition and/or damage. If the brake pedal pushrod and/or the brake pedal is misaligned, bent or damaged, go to step 11 . If the brake pedal pushrod and/or the brake pedal is not misaligned, bent or damaged, go to step 13 .
Replace the brake pedal pushrod and/or the brake pedal, as necessary. See BRAKE PEDAL ASSEMBLY under REMOVAL & INSTALLATION. If the replacement was completed, go to step 13 .
Replace the vacuum brake booster. See POWER BRAKE BOOSTER under REMOVAL & INSTALLATION. If the replacement was completed, go to step 13 .
Install or connect any components that were removed or disconnected during diagnosis. If the operation was completed, the brake assist system is okay. If the operation was not completed, see SYMPTOMS (HYDRAULIC BRAKES) .