Initial Inspection and Diagnostic Overview
Inspection and VerificationPreliminary Checks
WARNING: Use of any brake fluid other than approved DOT 3 will cause permanent damage to brake components and will render the brakes inoperative. Brake fluid contains polyglycol ethers and polyglycols. Avoid contact with eyes. Wash hands thoroughly after handling. If brake fluid contacts eyes, flush eyes with running water for 15 minutes. Get medical attention if irritation persists. If taken internally, drink water and induce vomiting. Get medical attention immediately.
CAUTION: Brake fluid is harmful to painted or plastic surfaces. If brake fluid is spilled onto a painted or plastic surface, immediately wash it with water.
NOTE: Use clean, fresh Ford High Performance DOT 3 Motor Vehicle Brake Fluid C6AZ-19542-AB or equivalent meeting Ford specification ESA-M6C25A-A
^ Do not reuse brake fluid drained or bled from the system.
^ Do not use brake fluid that has been stored in an open container.
^ Do not use contaminated brake fluid.
NOTE: Prior to performing any diagnosis, make certain that the brake warning indicator is functional.
A change in brake pedal feel is usually the first indicator of a brake system concern. The change may only be normal ABS function, but is sufficient cause for further investigation. The brake warning indicator in the instrument cluster and the brake fluid level in the brake master cylinder reservoir are also indicators of system concerns.
If a wheel is locked and the vehicle must be moved, open a bleeder screw at the locked wheel to let out enough fluid to relieve the pressure. Close the bleeder screw. This bleeding operation may release the brakes but will not correct the cause of trouble. If this does not relieve the locked wheel condition, repair the locked components before proceeding.
Brake Booster
Inspect all hoses and connections. All unused vacuum connectors should be capped. Hoses and their connections should be properly secured and in good condition with no holes, soft or collapsed areas.
Road Test
Perform a Road Test to compare actual vehicle braking performance with the performance standards expected by the driver. The ability of the test driver to make valid comparisons and detect performance deficiencies will depend on experience.
The driver should have a thorough knowledge of brake system operation and accepted general performance guidelines in order to make good comparisons and detect performance problems.
Select a road that is reasonably smooth and level. Gravel or bumpy roads, except to demonstrate ABS function, are not suitable. The surface does not allow the tires to grip the road equally. Avoid crowned roads.
A key factor in evaluating brake concerns is the deceleration rate. This varies from vehicle to vehicle and with changes in operating conditions. It is evident how well the brakes are working after just a few applications.
Avoid locking the brakes. Locked brakes are not an indicator of braking efficiency.
Visual Inspection Chart
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.
For slow or incomplete brake pedal return concern:
^ Inspect for binding, damage, correct installation or interference at the brake pedal.
^ Cheek the power brake booster for binding, damage and correct installation.
Vibration When Brakes are Applied
For vibration concerns when brakes are applied, carry out the following procedure.
Visually inspect:
^ the suspension condition and tire pressure.
^ suspension bushings and ball joints.
Correct as necessary.
1. Verify and isolate the concern. Brake roughness can be felt in:
^ the steering wheel.
^ the seat.
^ the brake pedal.
2. After verifying the concern, cheek for related concerns in the:
^ On-Line Automotive Service Information System (OASIS).
^ Technical Service Bulletins.
3. Check wheel bearing end-play and correct as necessary.
NOTE: Begin at the front of the vehicle unless the vibration has been isolated to the rear.
4. Remove the tire and wheel.
5. Remove the brake caliper.
6. Measure and record the brake disc thickness. If the thickness before machining is not greater than 0.6 mm (0.02 inch) above the minimum thickness specification molded into the brake disc, install a new brake disc. Do not machine a new brake disc.
7. For vehicles with a two-piece hub and brake disc assembly:
^ Match-mark before disassembly.
^ Remove the brake disc.
^ Using a die grinder with a mild abrasive disc (Scotch Brite type), remove any rust or corrosion from the hub and brake disc mounting surfaces.
^ Align the match-marks and reinstall the brake disc on the hub.
8. CAUTION: Do not use a bench lathe to machine brake discs.
NOTE: The depth of cut must be between 0.10 and 0.20 mm (0.004 and 0.008 inch). Lighter cuts will cause heat and wear. Heavier cuts will cause poor brake disc surface finish.
Using a hub-mount brake lathe, machine the brake discs. Follow the manufacturer's instructions. After machining, make sure the brake disc still meets the thickness specification.
9. Using a dial indicator, verify that the brake disc lateral runout is now within vehicle specification.
10. Remove any metal chips.
11. Remove the brake lathe hub adapter.
12. Remove any remaining metal chips from the machining operation.
13. CAUTION: Do not carry out this step on rear drum-in-hat brake discs.
For vehicles with a two-piece hub and a non drum-in-hat brake disc assembly:
^ Remove the brake disc from the hub.
^ Remove any remaining metal chips from hub and brake disc mounting surfaces and from the ABS sensor.
^ Apply High Temperature Nickel Anti-Seize Lubricant F6AZ-9L494-AA or equivalent meeting Ford specification ESE-M12A4-A to the mounting surfaces.
^ Using the match-marks, mount the brake disc on the hub.
14. Install the caliper and check brake operation.