Brake Booster
Vehicles are equipped with a vacuum booster. Vehicles use a dual-diaphragm vacuum booster. The dual-diaphragm (tandem) vacuum boosters are self-contained, vacuum power brake units. Booster assists in actuating master cylinder push rod.
Booster contains either a single or dual vacuum-suspended diaphragm which uses engine manifold vacuum or atmospheric pressure for power.
A mechanically-operated booster check valve controls power brake application and release in relation to foot pressure applied to check valve operating rod. Booster check valve is the only serviceable component of brake booster assembly.
An equalizer valve links 2 chambers of brake booster. When valve opens, vacuum in chambers can equalize. When it closes, chambers are separated. A vacuum bleed valve functions to reduce amount of vacuum in chamber "B" When boost is required. See Fig 1 .