Initial Inspection and Diagnostic Overview
Inspection and VerificationPreliminary Checks
NOTE: Always check the fluid level in the brake master cylinder reservoir before carrying out the test procedures. If the fluid level is not at the correct level, fill the reservoir using the specified DOT 3 or DOT 4 brake fluid. Prior to carrying out any diagnosis, make certain that the brake warning indicator is functional.
The first indication that something may be wrong in the brake system is a change in the feeling through the brake pedal. 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 correctly secured and in good condition with no holes, soft or collapsed areas.
Road Test
Carry out 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 are not suitable because 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, incorrect installation or interference at the brake pedal.
^ Check the power brake booster for binding, damage and incorrect 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, check for related concerns in the:
^ Technical Service Bulletins.
3. Check wheel bearing end-play and correct as necessary.
4. NOTE: Begin at the front of the vehicle unless the vibration has been isolated to the rear.
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 (0.024 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 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 metal chips.
11. Remove the brake lathe hub adapter.
12. Remove any remaining metal chips from the machining operation.
13. For vehicles with a two-piece hub and 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 XL-2 (Canada CXG-2-B) 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.