1991 Mercury Grand Marquis Brake Service (ONLINE REPAIR MANUALS)

REMOVAL

Except Capri, Festiva, Tracer, Scorpio, XR4Ti, Probe & 1991 Escort

• Remove brake fluid until reservoir is half full.
• Raise and support front of vehicle, then remove wheel and tire assembly.
• Remove caliper locating pins.
• Lift caliper assembly from adapter plate, then remove outer shoe from caliper assembly.On some models, slip shoe down caliper leg until clip is disengaged.
• Remove inner shoe and lining assembly.On some models, pull shoe straight out of piston. This should require a force as high as 20-30 lbs.
• Suspend caliper from inner fender housing with wire to avoid damaging brake ...

Servicing of disc brakes is extremely critical due to the close tolerances required in machining the brake disc to insure proper brake operation.

The maintenance of these close controls of the shape of the rubbing surfaces is necessary to prevent brake roughness. In addition, the surface finish must be non-directional and maintained at a micro inch finish. This close control of the rubbing surface finish is necessary to avoid pulls and erratic performance and promote long lining life and equal lining wear of both left and right brakes.

In light of the foregoing remarks, refinis...

Remove wheels and inspect brake disc, caliper and linings. The wheel bearings should be inspected at this time and repacked if necessary. Do not get any grease on the linings.

If the caliper is cracked or fluid leakage through the casting is evident, it must be replaced as a unit.

Should it become necessary to remove the caliper for installation of new parts, clean all parts in alcohol, wipe dry using lint free cloths. Using an air hose, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon re...

BENDIX, TEVES & DOUBLE DIAPHRAGM BOOSTER

On Bendix, Teves and Double Diaphragm Booster type power brake units, overhaul is not required. If it has been determined that the brake booster is defective, replace power brake unit as an assembly. In some instances, the only service required is replacement of the check valve and grommet and pushrod adjustment.

SINGLE DIAPHRAGM BOOSTER

Disassembly

• Remove brake booster from vehicle.
• Place front shell of booster in a vise.
• Remove clevis from valve rod and plunger assembly.
• Remove dust boot from rear shell,Fig. , then place alignment marks on fron...

• Grease or any other foreign material must be kept off the caliper, surfaces of the disc and external surfaces of the hub, during service procedures. Handling the brake disc and caliper should be done in a way to avoid deformation of the disc and nicking or scratching brake linings.
• If inspection reveals rubber piston seals are worn or damaged, they should be replaced immediately.
• During removal and installation of a wheel assembly, exercise care so as not to interfere ...

Complaints about power brake operation should be handled as if two separate systems exist. Check for faults in the hydraulic system first. If it is satisfactory, start inspecting the power brake circuit. For a quick check of proper power unit operation, press the brake pedal firmly and then start the engine. The pedal should fall away slightly and less pressure should be needed to maintain the pedal in any position.

Another check begins with installation of a suitable pressure gauge in the brake hydraulic system. Take a reading with the engine off and the power unit not opera...