1994 Mercury Grand Marquis Brake Service (ONLINE REPAIR MANUALS)

On vehicles equipped with anti-lock brakes refer to appropriate "Anti-Lock Brakes".

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 hydr...

FRONT & REAR SPLIT SYSTEMS

When the brake pedal is depressed, both the primary (front brake) and the secondary (rear brake) master cylinder pistons are moved simultaneously to exert hydraulic fluid pressure on their respective independent hydraulic systems. The fluid displacement of the master cylinder is proportioned to fulfill the requirements of each of the two independent hydraulic brake systems, Fig. .

If a failure of a rear (secondary) brake system should occur, initial brake pedal movement causes the unrestricted secondary piston to bottom in the master cylinder bore. Primary p...

BRAKE ROUGHNESS

The most common cause of brake chatter on disc brakes is a variation in thickness of the disc. If roughness or vibration is encountered during highway operation or if pedal pumping is experienced at low speeds, the disc may have excessive thickness variation. To check for this condition, measure the disc at 12 points with a micrometer at a radius approximately one inch from the edge of the disc. If thickness measurements vary by more t...

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 requir...

The hydraulic system must be depressurized before disconnecting any hydraulic lines or fittings. Depressurize the system by pumping the brake pedal a minimum of 25 times with the ignition switch in the OFF position.

After performing any service work, obtain a firm brake pedal before moving vehicle.

MARK VII

Replacement

To remove shoe and lining assemblies, remove caliper as described under "Caliper Service." It is not necessary to disconnect the brake hose. After removing the caliper, support it with a length of wire to avoid damaging the brake hose. To replace the shoe and lining a...

MASTER CYLINDER

Except Capri, Escort, Sable, Taurus & Tracer

• On models equipped with ABS, depress brake pedal several times to exhaust all vacuum in the system.
• On all models, disconnect brake lines from master cylinder, then all necessary electrical connectors.
• On models equipped with ABS, disconnect hydraulic control unit supply hose at master cylinder. Secure hose in a position to prevent brake fluid loss.
• On all models, remove nuts retaining master cylinder to brake booster.
• Remove master cylinder.
• Reverse procedure to install. After installation is complete, fill master cyli...