The owner of a vehicle complains the car is hard to stop. The technician doing the diagnosis starts by pumping the brake pedal several times with the engine off, and then starts the engine while holding firm pressure on the brake pedal. The pedal falls away slightly and less pressure is needed to maintain the pedal in any position. What does this test prove?
A)The master cylinder is working.
B)The vacuum booster is working.
C)The front brakes require adjustment.
D)There is air in the hydraulic system.

Question

Quizplus · Accepted Answer

This test proves that the vacuum booster is working. When the engine is started and the brake pedal falls away slightly while less pressure is needed to maintain its position, it indicates that the vacuum booster is providing the expected power assist to the braking system.

The Owner of a Vehicle Complains the Car Is Hard