Q: How to remove and inspect the brake discs on a Lincoln Navigator equipped with air suspension?
A: If the vehicle is equipped with air suspension, turn off the air suspension system. The switch is located in the area of the right kick panel. Loosen the wheel lug nuts, raise the vehicle and support it securely on jackstands. Apply the parking brake. Remove the wheels. Visually inspect the disc surface for score marks and other damage. Light scratches and shallow grooves are normal after use and won't affect brake operation. Deep grooves - over 0.015-inch(0.38 mm) deep - require disc removal and refinishing by an automotive machine shop. Be sure to check both sides of the disc. To check disc run out, place a dial indicator at a point about 1/2- inch from the outer edge of the disc. On 4WD model front discs and all rear discs, install the lug nuts, with the flat sides facing in, and tighten them securely to hold the disc in place. Set the indicator to zero and turn the disc. If it does, the disc should be refinished by an automotive machine shop. The manufacturer recommends resurfacing the brake discs only in the event of pedal pulsations or hard (overheated) spots on the disc. If you elect not to have the discs resurfaced, deglaze them with sandpaper or emery cloth. The disc must not be machined to a thickness less than the specified minimum thickness, which is cast into the disc. The disc thickness can be checked with a micrometer. Remove the Brake Calipers (don't disconnect the brake hoses) and hang them out of the way. If you're removing a front disc, remove the caliper anchor bracket. On 2WD model front discs, remove the grease cap, wheel bearing retainer nut, spindle nut, outer bearing retainer washer and outer wheel bearing, then remove the disc/hub. On 4WD model front discs and all rear discs, simply remove the lug nuts installed and pull the disc off the hub. Installation is the reverse of removal. Lower the vehicle and reactivate the air suspension system, if equipped. Tighten the wheel lug nut.