Description

Brake Servo – vacuum brake booster mounted on the bulkhead between the brake pedal and the brake master cylinder.

Vacuum is applied to one side of the servo diaphragm while atmospheric pressure acts on the other, drawn from the inlet manifold on petrol applications and from a dedicated vacuum pump on diesel applications. The resulting pressure difference multiplies the driver’s pedal effort before it reaches the master cylinder pushrod, so full braking pressure is achieved with moderate pedal force.

A failed servo gives a hard pedal with poor retardation, a hiss from the bulkhead as the pedal is pressed, or an unstable idle where a split diaphragm draws air into the intake. Supplied as a complete servo unit; the master cylinder is a separate part.