310T Engine And Supporting Systems Practice Exam

How does a vacuum-assisted brake booster affect braking effort?

It uses atmospheric pressure to lighten pedal effort. It reduces braking force. It has no effect on pedal effort. It uses engine vacuum to amplify braking force, reducing pedal effort.

Correct Answer:

It uses engine vacuum to amplify braking force, reducing pedal effort.

Explanation:

Vacuum-assisted brakes lighten pedal effort by using engine vacuum to boost the force you apply. Inside the booster, a diaphragm is exposed to vacuum on one side and atmospheric pressure on the other. When you press the brake, a valve shifts so that the booster adds force to the master cylinder push rod from the pressure difference across the diaphragm. This makes the master cylinder piston move with more total force than your foot alone would provide, so you get the same braking effect with less pedal effort. If vacuum is lost (engine off or leak), the pedal becomes stiffer because the booster can’t provide that extra assist.

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