How do I Test a Power Brake Booster For a 1971 Chevelle?

Chevrolet first introduced the Chevelle in 1964. Auto enthusiasts quickly found the Chevelle to be a tinker's dream, and Chevrolet was quick to introduce a number of sportier versions to take advantage of the muscle car image. The 1971 Chevelle was part of the second generation design, and power front disc brakes were offered as part of the optional SS package. The power brakes were state-of-the-art in 1971, however the design was fairly rudimentary by today's standards. The heart of the system was a power booster that used a vacuum generated in the engine intake manifold to assist the driver in braking. Testing this type of booster is a simple task that drivers can easily do themselves.

Instructions

1

Park your Chevelle and allow the engine run quietly at idle for a minute or so. Depress the brake pedal, and hold it down with steady force. Now turn the engine off. Continue to hold the brake pedal down for about 30 seconds while paying close attention to the pedal position. The pedal should remain in a steady position. If the pedal slowly rises it means that there is a leak in the system that is causing the power booster to lose vacuum.

2

Keep the engine off and pump the brake pedal a few times to use up any vacuum left in the booster with the engine still off. Depress the brake pedal and hold it down with steady force. Start the engine, paying close attention to changes in the pedal position as you do so. The brake pedal should drop slightly when the engine starts. If it does not, then the booster is not receiving vacuum from the engine intake manifold.

3

Allow the engine to run at idle for a minute or so. Shut the engine off and immediately pump the brake pedal a few times, waiting a few seconds between each pump. Pay close attention to the position that the brake pedal stops at with each successive pump. The pedal should stop at a slightly higher position with each pump, for at least the first three or four pumps. If the pedal stops at a low position with the first pump and then stops at the same high position on all successive pumps it means the booster is leaking and loosing vacuum.