GM 18015786 BOOSTER A

In normal use, the power brake booster has vacuum on both sides of its diaphragms, but when brakes are pushed, each diaphragm receives atmospheric air to help you stop. When the brakes get released, one side closes off vacuum air and draws air from the booster through the check valve to reach the vacuum source. The interior pieces of the part are both impossible to repair and not swappable with other parts. First disconnect the vacuum hose going to the vacuum check valve and negative battery cable, then take off the master cylinder mounting nuts and slide the master cylinder forward without unplugging the brake lines. Start by taking off the soundproofing from where the booster studs join if your car has that feature. Then you'll need to unscrew the mounting nuts for the booster. To take out the booster assembly from the car, first remove the pushrod from the brake pedal and use a slight downward tilt on the booster to keep the rod from being pushed sideways. To put the booster in place, apply the rubber gasket to the booster first, place the booster where it belongs, and connect the pushrod to the brake pedal while you ever so slightly tilt the booster into position. Unscrew the booster attachment nuts until they reach 15 ft. lbs. (21 Nm) for DeVille and Fleetwood, then install the optional noise reduction material, secure the master cylinder to the booster hard enough to lock with a torque of 20 ft. lbs. (27 Nm), join the vacuum hose to the air check valve, and wrap up with reconnecting the vehicle's negative power wire.