Brake disc — inspection, removal and installation
Inspection
1. Loosen the wheel lug nuts, raise the vehicle and support it securely on jack stands. Remove the wheel and install the lug nuts to hold the disc in place against the hub flange.
Note: If the lug nuts don’t contact the disc when screwed on all the way, install washers under them.
2. Remove the brake caliper as outlined in 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 two-mounting bracket-to-steering knuckle bolts (see illustration) and detach the mounting bracket.
i. 2 To remove the mounting bracket, remove these two bolts; be careful not to lose the pad support plates
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
i. 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 run-out limit. If it does, the disc should be refinished by an automotive machine shop.
i. 4a to check disc runout, mount a dial indicator as shown and rotate the disc
i. 4b Using a swirling motion, remove the glaze from the disc surface with sandpaper or emery cloth
Note: The discs should be resurfaced 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 related to questionable discs. At the very least, if you elect not to have the discs resurfaced, remove the glaze from the surface with emery cloth or sandpaper, using a swirling motion (see illustration).
5. It’s absolutely critical that the disc not be machined to a thickness under the specified minimum thickness. The minimum (or discard) thickness is cast or stamped into the inside of the disc (see illustration). The disc thickness can be checked with a micrometer (see illustration).
i. 5a the minimum thickness dimension is cast into the back side of the disc (typical)
i. 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 you’re removing a rear disc and it won’t come off, it may be interfering with the parking brake shoes; 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).
i. 6a If the rear disc is difficult to remove, remove this plug…
i. 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 to back the parking brake shoe away from the drum surface in the disc
Installation
7. Place the disc in position over the threaded studs.
8. Install the mounting bracket and caliper, tightening the bolts to the torque values listed in this Chapter’s Specifications.
9. Install the wheel, then lower the vehicle to the ground. 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. Bleeding won’t be necessary unless the brake hose was disconnected from the caliper. Check the operation of the brakes carefully before driving the vehicle.