Pinpoint Test J: Excessive/Erratic Brake Pedal Travel

1. Road test the vehicle on rough road conditions.
2. Apply the brakes slowly.

Is the brake pedal effort and brake pedal travel normal?

• Yes  : Vehicle is OK.
• No  : GO to  J2.

1. Check the brake master cylinder reservoir fluid level.

   Is the fluid level OK?

• Yes  : GO to  J3.
• No  : CHECK brake master cylinder reservoir sealing points. For additional information, refer to BRAKE MASTER CYLINDER  component test. ADD brake fluid and BLEED the brake system.

Refer to: Brake System Bleeding - Vehicles Without: Carbon Ceramic Brakes  (General Procedures). TEST the system for normal operation.

1. Run engine at idle speed.
2. Apply the brake pedal lightly three or four times.
3. Wait 15 seconds for the vacuum to replenish.
4. Push down on the brake pedal until it stops moving downward or an increased resistance to the brake pedal travel occurs.
5. Hold the brake pedal in the applied position while increasing the engine speed to 2000 revs/min.
6. Release the accelerator pedal.

Does the brake pedal move downward as the engine speed returns to idle?

• Yes  : GO to  J4.
• No  : CHECK the vacuum to the brake booster.

1. Check the front wheel bearing assembly.

   Are the front wheel bearings loose?

   • Yes  : INSTALL a new front wheel bearing if damaged.

     Refer to: Front Wheel Bearing and Wheel Hub - V8 N/A 4.2L Petrol/V8 S/C 4.2L Petrol or Front Wheel Bearing And Wheel Hub - V8 N/A 5.0L Petrol/V8 S/C 5.0L Petrol (Removal and Installation).

     TEST the system for normal operation.

   • No  : CHECK the front brake discs for thickness variances.