Brake Problem on my new to me 87

[zimmstoy]

Hey everyone,

Back againin the square body game. This time around I picked up an 87 GMC R2500 454 EFI Truck. She has been rode hard and put up wet. Still runs good. Trying to get a few minor things worked out.

The biggest thing bugging me on the truck is the brakes. When I start up and brake the first time they are almost too good (to the point that they lock up). After that intial brake, they get kind of soft on me. The first half of the pedal travel doesn't even slow the truck down. The second half of the pedal travel slows the truck down (not quick enough for me) and it never actually bottoms out.

My first thought was that this was something related to the booster being out. I had a hissing noise in the interior and had a problem like that in the past that the booster solved. Unfortunately this wasn't the case. After replacing the booster, the problem still exists. Previous owner says he did the brakes, master looks like its been there a while. There is also a fitting on the master that allows for an additional brake line that goes into the truck to a brake controller. I am planning on taking that out.

So my question is. Any ideas? Does this sound like the master failing, air in the lines or something else? Any advice / guidance is greatly appreciated.

Thanks!