1999 Mercury Grand Marquis Brake Service (ONLINE REPAIR MANUALS)

Master Cylinder Overhaul

Disassemble

• Clean outside of master cylinder thoroughly. Drain brake fluid from master cylinder.
• Remove stop bolt and pressure control valves, if equipped.
• Pry up on reservoir and remove it from master cylinder body.
• Remove fluid control valve, if equipped.
• Depress primary piston and remove snap ring from retaining groove at open end of bore.
• Remove primary and secondary piston assemblies from master cylinder. If secondary piston does not come out, apply air pressure to secondary outlet port to remove.

Inspection

When disassembled, wash all parts in clean brake...

Battery Ground Cable

Prior to service, disconnect battery ground cable and isolate as required.

System Depressurizing

On models equipped with anti-lock brakes, hyd...

Pressure bleeding is recommended for all hydraulic disc brake systems.

Do not use brake fluid drained from the hydraulic system when bleeding the brakes. Ensure disc brake pistons are returned to their normal positions and the shoe and lining assemblies are properly seated. Before driving the vehicle, inspect the brake operation.

Do not shake the pressure bleeder tank while air is being added or after it has been pressurized. This will prevent air from the tank getting into the lines. Set the tank in the required location, then bring the air hose to the tank. Do not move the ta...

Pushrod

Proper adjustment of the master cylinder pushrod is necessary to ensure proper operation of the power brake system. A pushrod that is too long will prevent the master cylinder piston from completely releasing hydraulic pressure, eventually causing the brakes to drag. A pushrod that is too short will cause excessive brake pedal travel and cause groaning noises to come from the booster when the brakes are applied. A properly adjusted pushrod that remains assembled to the booster with which is was matched during production should not require service adjustment. However, if the b...

Whenever new brake components are installed in the hydraulic system, it is recommended that the entire hydraulic system be thoroughly flushed with clean brake fluid.

It may sometime become required to flush out the system due to the presence of mineral oil, kerosene, gasoline, etc., which will cause swelling of rubber piston cups and valves and render them inoperative.

Flushing is performed at e...

Disc brake service is critical due to the close tolerances required in machining the brake disc to ensure proper brake operation.

Maintaining close control of the shape of the rubbing surfaces is required to prevent brake roughness. In addition, the surface finish must be non-directional and maintained at a micro-inch finish. This is required to avoid pulls and erratic performance and promote long lining life and equal lining wear of both the lefthand and righthand brakes.

Do not attempt to refinish the rubbing surfaces unless precision equipme...