Hydraulic Brake Booster: Description and Operation

Fig. 1 Cross-sectional View Of Bendix Hydro-Boost Unit:

The Hydro-Boost system, Fig. 1, provides an additional cylinder in the brake system. This cylinder contains no brake fluid. The Hydro-Boost cylinder is hydraulically operated, by pressurized fluid from the power steering pump, providing power assist to operate a dual master cylinder brake system.
The booster is composed of two sections; the linkage section and the power section.
The booster is designed so that if a total absence of power assist occurs, the brakes can be applied manually, but somewhat greater pressure on the brake pedal is required.