over a week ago i had a brake light come on, and lost the pedal. so today i changed the master out for a new one(not a reman). no dice, still have the light and still have no rear brakes. i have the 13x3" shoes in the rear on a 14Bsf axel. and it worked fine when i put it on. i have no wet spots on the frame, and no obvious leaks. calipers in front are dry, rear backing plates are dry, no fluid seaping out of the drums, and it has been sitting for over a week since the problem occured. i am going to go out and see how far out of adjustment the rear shoes are, and if that helps. i just want to get people thinking about it so i can figure it out when it turns out not to be the rear shoes(enter murphy's law). so if a prop. valve does go bad, what does it do and how do i tell. and is there any way to check the vaccume booster?