Component Tests and General Diagnostics
Brake System Inspection
Material(s)
Brake Pads
NOTE: It is not required to install new brake pads when the brake discs are machined.
1. Inspect the brake pad friction material for contamination.
- If the friction material shows evidence of contamination, install new brake pads. REFER to Brake Pads for the front brake pads or REFER to Brake Pads for the rear brake pads.
2. Inspect and measure the thickness of the brake pad friction material. REFER to General Specifications .
- Minor surface cracks do not require pad replacement, however, if there are missing chunks or cracks in the lining through to the backing plate, install new brake pads. REFER to Brake Pads for the front brake pads or REFER to Brake Pads for the rear brake pads.
- If the thickness of the friction material is less than the specified thickness, install new brake pads. REFER to Brake Pads for the front brake pads or REFER to Brake Pads for the rear brake pads.
- If the friction material shows taper wear that is not within specifications, install new brake pads and verify the caliper guide pins are functioning correctly. REFER to Brake System Inspection.
Brake Disc
NOTICE: Using an impact tool without a torque socket leads to unevenly tightened wheel nuts. This causes brake disc on-vehicle lateral runout and brake roughness.
1. Inspect the brake discs and measure the brake disc thickness. Record the measurement, REFER to General Specifications .
- If the brake disc is cracked or otherwise damaged, install a new brake disc. REFER to Brake Disc for front brakes or REFER to Brake Disc for rear brakes.
- If the measurement is below the minimum thickness specification, install a new brake disc. REFER to Brake Disc for front brakes or REFER to Brake Disc for rear brakes.
- If the diagnosis has revealed vibration in the steering wheel, seat or pedal while braking that varies with vehicle speed, machine the brake disc. Heavily scored brake discs, similar to that caused by pads worn down to the backing plate, should also be machined. In order to machine, discs must be above the minimum thickness specification. REFER to General Specifications and REFER to Brake Disc Machining .
Brake Caliper
1. Inspect the brake calipers for leaks, damage to seals and piston corrosion or binding.
- If the brake caliper is leaking or otherwise damaged, install a new brake caliper. REFER to Brake Caliper for front brake calipers or REFER to Brake Caliper for rear brake calipers.
Brake Caliper Guide Pins
1. The guide pins should slide with a reasonable amount of hand force. If the brake pads show taper wear or the guide pins are difficult to move, carry out the following steps.
- Disassemble the brake caliper guide pins and inspect the guide pins and guide pin bores for wear, damage and corrosion. If bore is worn or damaged, replace the damaged component.
- Use a wire brush, rolled-up sandpaper or emery cloth to remove all corrosion and foreign material from the caliper guide pin bores. Clean any remaining foreign material from the bores with brake parts cleaner and compressed air.
- Assemble the caliper seals, boots and guide pins. Use an ample amount of the specified grease to lubricate the bores and guide pins.
- Inspect the brake pads. REFER to Brake System Inspection.
Brake Flexible Hose
NOTICE: Never use copper tubing. It is subject to fatigue, cracking and corrosion, which may result in brake tube failure.
NOTE: Double-wall steel tubing is used throughout the brake hydraulic system. All brake tube fittings must be correctly double flared to provide strong, leakproof connections. When bending tubing to fit the underbody or rear axle contours, be careful not to kink or crack the tube.
1. Inspect brake tubes for corrosion, cracks, leaks or any other signs of damage.
- If a section of the brake tube is damaged, replace the entire section with a new tube of the same type, size, shape and length.
- When installing the hydraulic brake tubing, hoses or connectors, tighten all connections to specifications. After installation, bleed the brake system. REFER to Brake System Bleeding .
2. Inspect the brake flexible hoses for cracks, leaks and swelling during brake application or any other signs of damage.
- Install a new brake flexible hose if the hose shows signs of softening, cracking or other damage. REFER to Brake Flexible Hose for the front brake flexible hose or REFER to Brake Flexible Hose for the rear brake flexible hose.
Brake Master Cylinder
NOTE: During normal operation of the brake master cylinder, the fluid level in the brake master cylinder reservoir falls during brake application and rises during release. The returning brake fluid creates a slight turbulence in the master cylinder reservoir. This is a normal condition and indicates that the compensator ports are not clogged. Clogged compensator ports may cause the brakes to hang up or not fully release. The net fluid level (such as after brake application and release) will remain unchanged. Fluid level will decrease with pad wear.
NOTE: A trace of brake fluid will exist on the booster shell below the master cylinder mounting flange. This results from the normal lubricating action of the master cylinder bore and seal.
1. Inspect the brake master cylinder for fluid leaks.
- Install a new master cylinder or brake fluid reservoir if signs of excessive leaking are present. REFER to Brake Master Cylinder .
- To check for correct brake master cylinder operation, REFER to COMPONENT TEST(S) Testing and Inspection.
Brake Booster
1. Inspect the brake booster for excessive corrosion or damage. Inspect the vacuum hoses for leaks and kinks.
- Install a new brake booster if signs of excessive corrosion or damage is found. REFER to Brake Booster .
- Repair or replace vacuum hoses as necessary.
- To check for correct brake booster operation, REFER to Brake Booster Brake Booster.