I am trying to get the brakes working good again on my '89 chevy k1500. I have gone through two autozone master cylinders now along with one napa one (re-man'd) and the pedal is still going to the floor. My dad made the mistake tonight of pushing the MC all the way in when bench bleeding it, which the instructions say not to do. (I didn't do that on the first two!!) My question is why not? I measured the distance the pedal pushes it in and that is the exact same as how far it is possible to push it in when its on the bench, so what gives? I wonder if that is the problem with my reman'd napa this time around? The only thing I can think of is when you push it all the way in the seals are getting torn up, is there any insight into my problem? I bled the heck out of the lines and its not leaking fluid, whats the problem?