How the brake servo works

The brake servo, also known as the brake booster, plays a pivotal role in reducing the physical effort needed to apply the vehicle’s brakes. In its resting state, or when the brakes are not engaged, both sides of the servo’s diaphragm are subjected to the vacuum pressure created by the engine’s inlet manifold. This equilibrium ensures that the diaphragm remains stable and ready to assist in braking when needed.

Upon applying the brake pedal, the system allows outside air to enter behind the diaphragm. This inflow of air alters the pressure dynamics, creating a differential that pushes the diaphragm forward. As the diaphragm moves, it exerts force against the master cylinder piston. This action amplifies the driver’s input, translating a modest press of the brake pedal into a substantial hydraulic force, which then efficiently slows down or stops the vehicle.