Brake Booster
WARNING: This page is about a different car, the 2004 Ford Escape, 2003 Ford Escape, and 2002 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The brake booster consists of a power brake booster, vacuum booster hose and power brake booster check valve. The power brake booster reduces the effort required to push the brake pedal to actuate the brakes. The vacuum booster hose supplies vacuum to the brake booster. The vacuum booster check valve closes when the engine is turned off and traps engine vacuum in the power brake booster.