Which part of power brakes uses the engine to create a vacuum?

The power booster is the correct answer because it is specifically designed to utilize vacuum created by the engine to assist in braking. When a driver presses the brake pedal, the power booster enhances the force applied by the driver, making it easier to stop the vehicle. This vacuum assist reduces the amount of physical effort needed to apply the brakes, improving overall control and responsiveness.

The master cylinder is responsible for creating hydraulic pressure in the braking system, but it does not generate vacuum; instead, it works in conjunction with the power booster to operate the brakes more efficiently. The hydraulic actuator is involved in converting hydraulic pressure into mechanical movement to apply the brakes, but it also does not generate vacuum. The pinion gear has a different function related to steering mechanisms and is not relevant to the vacuum creation in the braking system. Thus, the power booster is crucial in utilizing the engine's vacuum to enhance braking effectiveness, confirming its role in this context.