what is a brake booster

A brake booster is a device that amplifies the force applied on the brake pedal when transferring that force to the brake master cylinder. It is a component used in motor vehicles in their braking system to provide assistance to the driver by decreasing the braking effort. The brake booster is what separates power-assisted brakes from manual ones. The most common type of brake booster is the vacuum brake booster, which uses engine vacuum to amplify the pressure applied on the brake pedal. The vacuum brake booster is usually mounted on the firewall in the engine compartment and has a chamber divided in half by a diaphragm. The chamber is connected to a vacuum source, usually the intake manifold, and it has a shaft with valves running through the center. The brake pedal is linked to one side of the booster, and the master cylinder is mounted on the other side. When the brake pedal is pushed, the shaft moves forward and opens the valve on the back of the chamber, allowing atmospheric pressure to enter half of the chamber, while the other half of the chamber is still under vacuum. The difference in pressure moves the shaft forward even more, pressing on the master cylinder pushrod and amplifying the force applied on the brake pedal. When the pedal is released, a spring returns the shaft to its starting point, and vacuum is equalized on both sides of the diaphragm.