Vacuum servo

Brake booster from a Geo Storm.
Brake vacuum servo section

A vacuum servo is a component used on motor vehicles in their braking system, to provide assistance to the driver by decreasing the braking effort. In the US it is commonly called a brake booster.

A vacuum servo, also known as a power booster or power brake unit, uses a vacuum, usually supplied by the engine, to multiply the driver's pedal effort and apply that effort to the master cylinder. [1]

Because the servo depends on the vacuum supplied by a running engine, a check valve is typically used in the vacuum line to maintain residual vacuum without engine support, allowing limited use even after parking.

  1. ^ "Brakes - Hydraulic - EduMech". www.edumech.co.uk. Archived from the original on 2016-04-25. Retrieved 2016-04-25.