Vacuum Brake Booster: Description and Operation
POWER BOOSTERThe power booster is a single diaphragm, vacuum operated unit. When the service brakes are not applied, there is no power assist because equal pressure (vacuum) exists on both sides of the power booster diaphragm. When the brakes are applied, vacuum is present on one side of the diaphragm, and air, at atmospheric pressure, is admitted to the other side. Power assist is provided when there is unequal pressure on opposite sides of the diaphragm. When the brakes are released, atmospheric pressure is shut off, and the vacuum source creates equal pressure on both sides of the diaphragm by means of a one-way valve in the power booster.