The brake booster (also referred to as a servo across ... enters via a valve on the side facing the brake pedal. A one-way check valve prevents this atmospheric pressure from entering the vacuum ...

Engaging the brake pedal opens a valve, and air is drawn into one side of the booster. This allows the ... as it normally ...

According to NHTSA, "Incorrect material composition of the brake booster check valve may cause the check valve to stick closed when the engine is shut off." As a result, when affected vehicles are ...