When the engin e is running you have vacuum or someother power supply to give power to power brakes. Whe it is off there is only enough power left to give one, maybe two hits of the brake pedal. They will still work only will be hard to push down. If they are broke when engine is off then they will be with engine running as well.
August, 27, 2012 AT 5:41 PM
After engine is stopped, the first two strokes of the pedal should be soft with assist but if it is hard immediately, you have a vacum leak with the booster.