C-30 Brakes Locking Up

[dustykey]

Just bought an 86 C-30 with a 454. The brakes lock up on the first two or three applications in the morning or after the truck has been sitting for a few hours and then it quits. There were some front brake problems from the start, so I replaced the calipers, pads and rubber hoses. It does have a hydro booster on it and that is leaking a bit. I'm not sure if I have master cylinder problem, a prop valve problem or a hydro booster problem. Any help would be great......thanks.