Vacuum Test

To test the brake vacuum system, start and run the engine for 10 seconds at fast idle. Stop the engine and let stand for 5 minutes, then depress the brake pedal with approximately 89 N (20 pounds) of force.

The brake pedal feel (brake application) should be the same as that noted with the engine operating. If the brake pedal feels hard (no power assist), repeat the test and listen for air leaks. Air leaks can occur at the vacuum booster hose connections, vacuum hose check valve, the hose itself and in the power brake booster. Replace or repair the defective component.