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.

[Oldriginal86]

Front or rear or all wheels locking up?

[donut]

My question also.
You did the fronts, plan on at least checking the rear. IMO, they don't wear as much, but due to the effort required to pull a drum, they're usually neglected.

Curious, does it go away if you drag the brakes for a little bit and get some heat in them?

Asking as mine get "touchy", especially if sitting for a while, (weeks). If it does sit, dragging them for a few hundred feet usually cures this. My fronts have been rebuilt, including rotors, and the rears have been inspected. Master cylinder has been replaced (bad when I bought the truck), hydroboost drips...sound familiar?

[dustykey]

All wheels locking up. I usually back up and pull forward a few times in my yard and then they stop. I do kind of gather a bit of speed and drag them a bit in the yard. After all of that they are great.

[NASTY-LSX]

My 85 k20 does that when I first get in it, once warm they work perfect.