Ford: Braking, vacuum booster, f 350

Question
I have a 1995 7.3 turbo diesel F-350. My problem is that when I have been driving for a little bit I can touch my brake pedal and it goes down on it's own. I have replaced the Master Cylinder already and made sure the brakes were bled thoroughly. Most of the time if I push in the clutch the brake pedal will go back to normal position. Your information would be greatly appreciated. Thanks,  Drew

Answer
Hello.


You have a problem with the power assist portion of the brakes.

It is not a common problem, so i cannot say exactly what caused it, but I have to assume that you have a Vacuum Booster and the valving has failed internally.  Replace the booster.