The power brake booster unit requires no special maintenance apart from periodic inspection of the vacuum hose and the case. Dismantling the brake booster requires special tools and should not be attempted by the home mechanic; if a problem arises, a new or factory rebuilt unit should be installed. To check the power booster, begin by depressing the brake pedal several times with the engine running, ensuring no change in the pedal reserve distance, which is the distance between the pedal and the floor when fully depressed. After turning off the engine, slowly depress the brake pedal; if it goes down farther initially but rises after subsequent depressions, the booster is airtight. Depressing the pedal and starting the engine should result in a slight drop of the pedal for normal operation. If the pedal remains depressed for about 30 seconds without a change in reserve distance after stopping the engine, the booster is airtight. A "hard" pedal when the engine is running indicates improper booster operation or a vacuum leak in the hose. For removal, detach the master cylinder from the booster, being cautious not to bend the brake lines, and unplug the electrical connector from the brake light switch and cruise control switch if equipped. Remove the pushrod retaining clip and nylon washer, then detach the booster from the firewall and lift it out of the engine compartment. For installation, position the booster on the firewall, tighten the mounting nuts, connect the pushrod and brake light switch, and install the master cylinder, ensuring proper torque. Before driving, check the operation of the brakes. Some boosters may have an adjustable pushrod, typically matched at the factory, but if adjustment is needed, a gauge can be fabricated from heavy gauge sheet metal. Symptoms of a misadjusted pushrod include dragging brakes or excessive brake pedal travel with a groaning sound. To check the pushrod length, unbolt the master cylinder and position it aside without disconnecting hydraulic lines. Apply vacuum to the booster with a hand-held vacuum pump, then use the pushrod gauge to ensure proper seating of the pushrod. Adjust as necessary, and after completing the adjustment, reinstall the master cylinder and verify proper brake operation before driving.
Posted by FordPartsGiant Specialist 
