Initial Inspection and Diagnostic Overview
Special ToolsPart 1 Of 2:
Part 2 Of 2:
Inspection and Verification
WARNING: Use of any brake fluid other than the approved DOT 3 will cause permanent damage to brake components and will render the brakes inoperative.
WARNING: 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: Do not spill brake fluid onto painted surfaces. If spilled, wipe up immediately.
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, clean the reservoir cap before removing, then add DOT 3 brake fluid.
NOTE: Prior to carrying out any diagnosis, make sure the red 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.
Inspect all hoses and connections. All unused vacuum connectors should be capped. Make sure hoses and their connections are correctly secured and in good condition with no holes, soft or collapsed areas.
Non-Pressure Leaks
The only part of the brake system that could have a brake fluid loss that does not appear when the system is under pressure is the brake master cylinder reservoir area. Brake fluid loss can be caused by a missing or poorly-fitted brake master cylinder filler cap, a punctured or otherwise damaged brake master cylinder reservoir, a missing or damaged brake master cylinder filler cap gasket, or by missing, damaged or poorly-fitted sealing grommets between the brake master cylinder and the brake master cylinder reservoir.
The brake master cylinder reservoir grommets are not separately serviceable and must be installed new as part of a new brake master cylinder reservoir.
NOTE: The wet appearance on the outer cover of rubber brake hoses is called "sweating". This is a normal condition for neoprene rayon braid hose. The sweating condition is not evidence of a brake fluid leak and will not result in a loss of pressure in the system.
Install a new flexible brake hose if the hose shows signs of softening, cracking or other damage.
When installing a new brake hose, position the hose to avoid contact with other vehicle components.
Road Test
The technician should have a thorough knowledge of the brake system operation and accepted general braking guidelines in order to detect any 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.
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 brake pedal mounting for looseness and correct installation. Check the brake booster and the brake master cylinder for loose mounting. Correct as necessary and retest the system for normal operation.
For a slow or incomplete brake pedal return concern:
^ inspect for binding, damage, correct installation or interference at the brake pedal.
^ check the 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:
^ tire condition and 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. Install a new brake disc if the brake disc thickness is less than 0.60 mm (0.024 inch) above the minimum thickness specification. This will make sure that the brake disc thickness will be above minimum thickness after it has been machined.
7. CAUTION: Do not use a bench lathe to machine brake discs.
NOTE: The depth of the 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 the special tool, machine the brake discs. Follow the manufacturer's instructions. After machining, make sure the brake disc still meets the thickness specification.
8. Using a dial indicator, verify that the brake disc lateral runout is now within specification.
9. Remove the special tool hub adapter.
10. Remove any remaining metal chips from the machining operation.
11. NOTE: Match-mark the brake disc and hub before removing the brake disc.
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 anti-seize lubricant to the mounting surfaces.
^ Using the match marks, mount the brake disc on the hub.
12. Install the brake caliper and check brake operation.
Brake Master Cylinder-Normal Conditions
The following conditions are considered normal and are not indications that the brake master cylinder is in need of service.
Condition 1: During normal operation of the brake master cylinder, the fluid level in the brake nester cylinder reservoir will rise during brake application and fall during release. The net fluid level (such as after brake application and release) will remain unchanged.
Condition 2: A trace of brake fluid will exist on the booster shell below the master cylinder mounting flange. This results front the normal lubricating action of the master cylinder bore and seal.
Condition 3: Fluid level will decrease with pad wear.
Brake Master Cylinder-Abnormal Conditions
Changes in brake pedal feel or travel are indicators that something could be wrong in the brake system. GO to Symptom Chart for abnormal condition diagnosis. Symptom Related Diagnostic Procedures
Adjustable Pedals
1. Verify the customer concern by operating the adjustable pedals.
2. Visually inspect for obvious signs of mechanical or electrical damage.
3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
4. If the scan tool does not power up, refer to the scan tool manual.
5. Carry out the DATA LINK DIAGNOSTIC TEST. If the scan tool responds with:
^ CKT914, CKT915 or CKT70-ALL ECUS NO RESP/NOT EQUIP, refer to Module Communications Network.
^ NO RESP/NOT EQUIP for Front Electronic Module (FEM), refer to Module Communications Network.
^ System passed, retrieve and record the continuous DTCs and carry out self-test diagnostics for the FEM.
6. If the DTCs retrieved are related to the concern, go to the FEM Diagnostic Trouble Code (DTC) Index. Front Electronic Module (FEM) Diagnostic Trouble Code (DTC) Index
7. If no DTCs related to the concern are retrieved, GO to Symptom Chart to continue diagnostics.
Electronic Parking Brake (EPB)
1. Verify the customer concern by operating the EPB system.
2. Visually inspect for obvious signs of mechanical or electrical damage.
3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
4. If the scan tool does not power up, refer to the scan tool manual.
5. Carry out the DATA LINK DIAGNOSTIC TEST. If the scan tool responds with:
^ CKT914, CKT915 or CKT70-ALL ECUS NO RESP/NOT EQUIP, refer to Module Communications Network.
^ NO RESP/NOT EQUIP for EPB module, refer to Module Communications Network.
^ System passed, retrieve and record the continuous DTCs and carry out self-test diagnostics for the EPB module.
6. If the DTCs retrieved are related to the concern, go to the Electronic Parking Brake (EPB) System Diagnostic Trouble Code (DTC) Index. Electronic Parking Brake System Diagnostic Trouble Code Index
7. If no DTCs related to the concern are retrieved, GO to Symptom Chart to continue diagnostics.