power brake troubles

not that simple as there are a set of check and bypass valves inside besides a diaphram. when you push the pedal only a few 1000/inch a port open up to allow the vacuum to assist the pedal draw action and when you release it closes that port and equalizes the vacuum on that side of the diaphram so the pedal can release. Also if the pushrods are not adjusted correctly it will cause problems (one is it activates brakes without being on pedal).