Vacuum Brake Booster: Description and Operation

Brake Booster-Hydro-Boost(R)
The Hydro-Boost(R) brake booster is a hydraulically operated brake booster powered by the power steering pump. The power steering pump provides the fluid pressure to operate both the power brake booster and the power steering gear.
A Hydro-Boost(R) reserve system (accumulator) stores sufficient fluid under pressure to provide at least 2 power-assisted brake applications in the event the power steering pump fluid flow is interrupted.
For low assist concerns on vehicles equipped with the Hydro-Boost(R) system.





The brakes can also be applied manually if the reserve system is depleted.
Model identification is stamped into the power brake booster housing near the power steering pressure hose.
Any leakage goes directly back to the power steering pump reservoir.

DESCRIPTION AND OPERATION
Brake Booster-Vacuum
The vacuum-type power brake booster:
^ is a dual diaphragm, vacuum assisted power brake booster.
^ reduces brake pedal force and travel distance.
^ is located on the LH side of the bulkhead in the engine compartment, between the brake pedal and the brake master cylinder.
^ is divided into separate chambers by the diaphragms.
^ will not operate if vacuum is restricted or if any of the vacuum related power brake components fail.
^ is installed as an assembly.

If the power assist fails, the brake system will continue to operate with increased brake pedal effort.

Hose and Check Valve
The power brake booster check valve:
^ is located on the front of the power brake booster.
^ is installed separately (install a new grommet when installing a new check valve).
^ is positioned between the power brake booster and the power brake booster hose.
^ closes when the engine is turned off.
^ in the closed position, traps engine vacuum in the power brake booster
^ retains vacuum to provide several power assisted brake applications with the engine off.