Buick 18060099 Power Brake Booster Assembly

The power brake booster unit requires no special maintenance apart from periodic inspection of the vacuum hose and case. To check operation, depress the brake pedal several times with the engine off to ensure there is no change in the pedal reserve distance. Starting the engine while depressing the pedal should result in a slight drop, indicating normal operation. For an airtightness check, start the engine and turn it off after one or two minutes, then depress the pedal several times slowly; if the pedal goes down farther initially but rises after subsequent depressions, the booster is airtight. While the engine is running, stopping it with the brake pedal depressed should show no change in pedal reserve travel after 30 seconds, confirming airtightness. For removal on 1988 through 1990 models, special tools are required, and if a problem arises, a new or factory rebuilt unit should be installed. Remove the nuts attaching the master cylinder to the booster and carefully pull it forward, avoiding bending the brake lines. Disconnect the vacuum hose from the power brake booster and from the passenger compartment, disconnect the power brake pushrod from the brake pedal. Remove the nuts attaching the booster to the firewall, then carefully lift the booster away. For 1991 and later models, the same removal process applies, with the addition of removing the cross-vehicle brace on 2002 models. Caution is advised for ABS equipped models through 1998, as the master cylinder should not be disconnected from the hydraulic modulator assembly. After disconnecting the vacuum hose, it may be necessary to remove components like the upper intake plenum or acoustic engine cover, depending on the engine type. Disconnect the brake pushrod from the brake pedal while preventing the pedal from moving to avoid damaging the brake switch. The booster is mounted to the firewall with a "cam-lock" bracket; use a screwdriver to pry the locking tab out of the notch. If the factory tool is unavailable, a large strap wrench or rubber fuel hose can be used to assist in removal. Rotate the booster counterclockwise to free it from the bracket, taking care not to damage the boot around the pushrod. Installation is the reverse of removal, ensuring the locking tab is seated in the firewall bracket slot, followed by careful testing of the brake operation before driving.

In the event of vacuum failure, such as when the engine is off, the brake pedal can still be applied, but it will require higher pedal pressure similar to a standard braking system.

Fully remove the four booster mounting nuts and carefully lift the unit out of the engine compartment.