1991 Ford Thunderbird Brake Service (ONLINE REPAIR MANUALS)

HYDRAULIC ACTUATION UNIT

The hydraulic actuation unit,Figs. and , consists of two sections, the master cylinder and brake booster, which are arranged in the conventional fore and aft sequence. The booster contains a control valve, located in a parallel bore above the master cylinder.

ELECTRIC PUMP ASSEMBLY

This system uses high pressure brake fluid stored in a hydraulic accumulator,Fig. , for power assist as well as for rear wheel braking. The accumulator is a gas filled pressure chamber that stores brake fluid up to 2600 psi. The fluid is pressurized by an electric motor driven...

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 ...

Never use copper tubing as a replacement for steel tubing. Copper tubing is subject to fatigue cracking and corrosion which could result in brake system

Steel tubing is used to conduct hydraulic pressure to the brakes. All fittings, tubing and hose should be inspected for rusted, damaged or defective flared seats. The tubing is equipped with a double flare/inverted seat or I.S.O. flare to insure more positive seating in the fitting. To repair or reflare tubing, proceed as follows:

DOUBLE FLARE/INVERTED SEAT

• Using the tool shown inFig. or equivalent, cut off the damaged seat or da...

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...

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

MARK VII

CALIPER, REPLACE

Removal

• Raise vehicle and support on safety stands, then remove tire and wheel assemblies.
• Disconnect fitting on rear brake tube from hose end fitting at frame mounted bracket and plug end of brake tube to prevent loss of fluid and entry of dirt. Remove horse shoe retaining clip from hose fitting and disengage hose from bracket.
• Disconnect parking cable from lever,Fig. , using care to avoid kinking or cutting cable or return spring, then remove retaining screw from cal...

These models are equipped with a four wheel anti-lock brake system (ABS),Fig. . The system prevents lockup by automatically modulating brake system pressure during an emergency stop situation.

By controlling wheel lockup, the vehicle's operator can maintain steering control and stop the vehicle in the shortest possible distance, under most driving conditions.

The ABS system controls the front brakes separately and th...