Power Brake Booster
There are 2 different power brake booster designs, although externally they appear the same. All models use a 8.07" (205 mm) tandem power brake booster. The 2 boosters are internally tuned differently depending on whether the vehicle is equipped with the standard front disc/rear drum brake combination or the optional front disc/rear disc brake combination. If the power brake booster requires replacement, be sure it is replaced with the correct part. The power brake booster can be identified by the tag attached to the body of the booster assembly. This tag contains the following information:
- The production part number of the power brake booster.
- The date it was built.
- The manufacturer of the part.
The power brake booster is vacuum-operated. The vacuum is supplied from the intake manifold on the engine through the power brake booster check valve. See Fig 2.
As the brake pedal is depressed, the power brake booster input rod moves forward. This opens and closes valves in the power brake booster, allowing atmospheric pressure to enter on one side of a diaphragm. Engine vacuum is always present on the other side. This difference in pressure forces the output rod of the power brake booster out against the primary piston of the master cylinder. As the pistons in the master cylinder move forward, hydraulic pressure is created in the brake system.
The power brake booster assembly mounts on the engine side of the dash panel. The booster input push rod connects to the brake pedal. A vacuum line connects the power brake booster to the intake manifold. The master cylinder is bolted to the front of the power brake booster. See Fig 1.