Sounds like your master cylinder is leaking internally.i have the same problem. when turning it whines when steeping on the brakes it whines. the pedal is stiff with engine off as it should be but very slowly goes down with very hard pressure applied to it. as it whines when i get to the bottom of the pedal stroke it pulses. the master cyliner and hydroboost unit were out of the truck on a bench for quite some time. no leaks in brake system. i bled the **** out of it numerous time still has the same problems. new ps pump but still whines. abs maybe not bleeding properly (no air came out of any lines)? this is a nightmare. does anyone know where to get a chiltons manual on a 2001 f350 powerstroke not the crappy haynes.