Vacuum Brake Booster: Description and Operation

Brake Booster

The power brake actuation system includes a vacuum source (engine manifold or vacuum pump), vacuum assisted brake booster, vacuum check valve and a vacuum supply tube. Vehicles equipped with 3.5L and 3.7L engines utilize engine manifold vacuum and vehicles equipped with 2.0L GTDI engines utilize an engine-mounted/cam-driven vacuum pump to supply vacuum.

Vacuum is delivered through the vacuum supply tube to the vacuum check valve. The vacuum check valve is a one-way valve that allows supplied vacuum to the booster then closes when the vacuum supply is removed. The vacuum is applied to a rubber diaphragm on the vacuum side of the brake booster chamber which then pulls the piston rod in when the brakes are applied to provide power assist, reducing the amount of effort required at the brake pedal to actuate the foundation brakes.