Initial Inspection and Diagnostic Overview

WARNING: USE OF OTHER THAN THE APPROVED DOT 3 BRAKE FLUID WILL CAUSE PERMANENT DAMAGE TO THE BRAKE COMPONENTS AND WILL RENDER THE BRAKES INOPERATIVE.

NOTE: If a vehicle with a locked wheel must be moved, loosen the bleeder screw to relieve pressure.

Always check brake fluid level and, if necessary, fill with Ford High Performance DOT 3 Brake Fluid C6AZ-19542-AB or equivalent DOT 3 fluid meeting Ford specification ESA-M6C25-A.

1. Most brake concerns that are not related to the electrical or anti-lock system are caused by leaks or mechanical problems in the base brake system.
- For low brake fluid concerns, fill the brake master cylinder reservoir, apply the brakes and inspect for leaks. If no leaks are found, the concern may be caused by caliper piston advance to compensate for disc brake pad wear.
- For mechanical concerns, such as pulling, vibration, drag or squeal, thoroughly inspect the base brake system for wear or damage. Repair as necessary.
- For lack of power assist concerns, inspect the vacuum system for leaks. Repair as necessary.

2. To determine if a concern is anti-lock related, disable the anti-lock system by disconnecting the connector on the brake fluid level sensor at the brake master cylinder reservoir. If the concern cannot be duplicated with the anti-lock system disabled, the concern is in the anti-lock system.

3. To test the operation of the brake warning light, do the following:
- Start the engine and observe the brake warning light. The brake warning light should light and then go out.
- With the key to RUN, apply the parking brake. The brake warning light should light and stay lit until the parking brake is released.

4. For premature rear wheel lockup concerns that are not anti-lock related, inspect and adjust the rear brakes. Retest the system.
5. If the concern persists, replace the brake master cylinder fluid control valve mounted in the rear outlet port of the brake master cylinder. Retest the system.
6. For "pedal bottoms out" concerns, check the brake pedal reserve.
- Operate the engine at idle with the transmission in either PARK or NEUTRAL.
- Depress the brake pedal lightly three to four times.
- Allow 15 seconds for vacuum to replenish the power brake booster.
- Apply the brake pedal until it stops moving downward or an increased resistance to the brake pedal travel occurs.

NOTE: Increased resistance may feel like the brake pedal has bottomed out.

- Hold the brake pedal in the applied position and raise the engine speed to approximately 2000 rpm.
- Release the accelerator pedal and shaft and observe that the brake pedal moves downward as the engine returns to idle speed.

NOTE: The additional movement of the brake pedal is the result of the increased engine manifold vacuum which exerts more force on the power brake booster during engine rundown. This means that additional stroke is available in the brake master cylinder and the brake system is not bottoming out as a customer may believe.

7. For low or spongy brake pedal concerns:
- Check and, if necessary, refill the brake master cylinder reservoir.
- Bleed the brake system and retest the brake pedal feel.
- If the brake pedal is still low or feels spongy, check the wheel bearings.

8. For slow or incomplete brake pedal return concern:
- Inspect for binding, damage, correct installation or interference at the brake pedal.
- Check the power brake booster for binding, damage and correct installation.

9. For a vibration concern when the brakes are applied on a vehicle with rear drum brakes:
- Road test the vehicle.
- Apply the parking brake and note if vibration is felt.
- If vibration can be felt while applying only the parking brake, machine the brake drums if final internal diameter will be within specification. Retest the vehicle for normal operation.
- If vibration is only felt while applying the brake pedal, use a hub-mount brake lathe to machine the front disc brake rotors. Retest the vehicle for normal operation.