Brake disc — inspection, removal and installation
Inspection
1. Loosen the wheel lug nuts, raise the vehicle and support it securely on jackstan6. Remove the wheel and install the lug nuts to hold the disc in place. If the rear brake disc is being worked on, release the parking brake.
2. Remove the brake caliper as outlined in Section Disc brake caliper — removal and installation. It isn’t necessary to disconnect the brake hose. After removing the caliper bolts, suspend the caliper out of the way with a piece of wire. Remove the caliper mounting bracket bolts and detach the caliper mounting bracket.
3. Visually inspect the disc surface for score marks and other damage. Light scratches and shallow grooves are normal after use and may not always be detrimental to brake operation, but deep scoring requires disc removal and refinishing by an automotive machine shop. Be sure to check both sides of the disc (see illustration). If pulsating has been noticed during application of the brakes, suspect disc runout.
6.3 The brake pads on this vehicle were obviously neglected, as they wore down completely and cut deep grooves into the disc wear this severe means the disc must be replaced
4. To check disc runout, place a dial indicator at a point about 1/2-inch from the outer edge of the disc (see illustration). Set the indicator to zero and turn the disc. The indicator reading should not exceed the specified allowable runout limit. If it does, the disc should be refinished by an automotive machine shop.
6.4a Use a dial indicator to check disc runout ; if the reading exceeds the maximum allowable runout limit, the disc will have to be machined or replaced
6.4b Using a swirling motion, remove the glaze from the disc surface with sandpaper or emery cloth
Note: Professionals recommend resurfacing the discs whenever the pads are replaced regardless of the dial indicator reading, as this will impart a smooth finish and ensure a perfectly flat surface, eliminating any brake pedal pulsation or other undesirable symptoms. At the very least, if you elect not to have the discs resurfaced, remove the glaze from the surface with sandpaper or emery cloth using a swirling motion (see illustration).
5. It’s absolutely critical that the disc not be machined to a thickness under the specified minimum allowable refinish thickness. The minimum wear (or discard) thickness is cast into the inside of the disc (see illustration). The disc thickness can be checked with a micrometer (see illustration).
6.5a the minimum wear dimension is cast into the back side of the disc (typical)
6.5b Use a micrometer to measure disc thickness
Removal
6. Remove the lug nuts that were put on to hold the disc in place and slide the disc off the hub. If the rear disc won’t come off, it may remove the plug (see illustration) and rotate the adjuster to back the parking brake shoes away from the drum surface within the disc (see illustration).
6.6a If the rear disc is difficult to remove, remove this plug.
6.6b … insert a screwdriver through the hole (the hole must be at the 6 o’clock position, because that’s where the adjuster is located) and rotate the adjuster
Rotate the adjuster wheel in a clockwise direction (as seen from the front of the vehicle) to back off the parking brake shoes.
Installation
7. Place the disc in position over the threaded studs.
8. Install the caliper mounting bracket, tightening the bolts to the torque listed in this Chapter’s Specifications.
9. Install the caliper, tightening the bolts to the torque listed in this Chapter’s Specifications. Bleeding won’t be necessary unless the brake hose was disconnected from the caliper.
10. Install the wheel and lug nuts. Lower the vehicle and tighten the lug nuts to the torque listed in the Tune-up and routine maintenance Specifications. Depress the brake pedal a few times to bring the brake pads into contact with the disc. Check the operation of the brakes carefully before driving the vehicle.