1991 Ford Mustang Brake Service (ONLINE REPAIR MANUALS)

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...

• Lightly lubricate backing plate shoe contact surfaces with suitable brake lube.
• On type 1 brakes, assemble parking brake lever to secondary shoe and secure with spring washer and retaining clip. Crimp ends of clip with suitable pliers.On type 2 brakes, engage parking brake lever tang with secondary shoe.
• Position brake shoes on backing plate, primary (short lining) shoe facing front of vehicle and secondary (long lining) facing rear. Secure brake shoes with hold-down springs, pins and retainers.
• Install parking brake link and spring between shoes.
• Loosen parking brake adjustment nut, t...

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...

The vacuum assist diaphragm assembly multiplies the force exerted on the master cylinder piston in order to increase the hydraulic pressure delivered to the wheel cylinders while decreasing the effort necessary to obtain acceptable stopping performance.

Vacuum assist units get their energy by opposing engine vacuum to atmospheric pressure. A piston, cylinder and flexible diaphragm utilize this energy to provide brake assistance. The diaphragm is balanced with engine vacuum until the brake pedal is de...

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 ...

Pressure bleeding is recommended for all hydraulic brake systems.

The bleeding operation itself is fairly well standardized. First step in all cases is cleaning the dirt from the filler cap before removing it from the master cylinder. This should be done thoroughly.

Pressure bleeding is fastest because the master cylinder doesn't have to be refilled several times, and the job can be done by one man. To prevent air from the pressure tank getting into the lines, do not shake the tank while air is being added to the tank or after it has been pressurized. Set the tank in the required ...