i just restored my cuda, allnew wheel cylinders, shoes, but used the old master cylinder. i bled the brakes and all was working excellant. then it seemed like to more i used the brakes the more the pedal started not to want to go down. until all brakes locked up. i loosed the lines to the master and fluid came out and released the pressure on the brakes. ive seen where the master cylinder quits and you have no brakes, but i have not seen where the more you use the brakes the more brakes are applied and stay applied. i was going to buy a new master but i thought id drop a line and see what you guys think, thanks for your help