I am having an odd problem w/my brakes. I went to bleed them and my pedal has pressure for the first half of the throw/travel but then there is an audible "woosh" of air and the pedal falls to the floor on the second half of the pedal travel. I am going to pull the booster and take a look. Is it a simple matter a little air pressure type leak down bench test?.. Do the parameters change as the pedal travles?? Will it successfully test w/out pressure on the rod through the booster?... What to do,... what to do???...