Vacuum Brake Booster: Description and Operation

The vacuum booster is a single diaphragm vacuum suspended unit. Engine vacuum is provided to vacuum booster through a hose and a vacuum check valve. The one-way check valve is provided between engine and the booster to prevent a loss of booster vacuum when engine vacuum falls below that stored in booster. When brakes are not applied, internal valves within the booster provide vacuum to both sides of diaphragm. When brakes are applied, air at atmospheric pressure is applied to one side of the diaphragm. Since a higher pressure now exists on one side of diaphragm than the other, a force is created, assisting brake application.