1994 KW W900 wierd brake problems

I have a 1994 KW W900 with the Cat 3406B. Haven't had the truck running in well over 6 months and started it for the first time today, went to move it and realized that it's having some brake issues that won't let it move. Both air tanks fill up and kick off where they should and the applied brake pressure gauge spikes to the 'danger zone' for no reason. The bobtail brake lights are on as well. The brake pedal is extremely stiff and sticks in whatever position it's in when you let off the pedal, in order to get it to come back up you have to pull it up by hand. Pumping the brake pedal, and trolley valve, has no effect on the brakes. The parking brakes will release but the service brakes are engaged on all 10 wheels.

I'm guessing that the foot valve has gone out or could it be something else?

 

This is not a straight truck. Went and looked up underneath at the underside of the cab where all of the air lines run to what I believe is the foot valve. I see a bunch of different lines, some large and some small and I haven't the foggiest idea what is what. Anywhere online that I could find a schematic that you know of? Thanks!

 

Gotcha, will give their site a try.

 

Got in there today and you just about hit the nail on the head, the little puck is stuck all the way down. Tried to pry it up with leverage and a chisel but had no real luck. There was a ton of dusty corroded gunk built up around it, I'm guessing that's part of the problem. Soaked it with PB Blaster and going to try again shortly.

As far as the brake puck/piston goes, are they usually splined or smooth all the way around? Just so I know what to expect when I get in there with the vice grip.

 

Looks like I might be needing a new foot valve. Locked the vise grip onto the puck and was not able to get it to rotate or do anything at all. There's a lip on the top of the plunger that I tried to use to get it up with leverage but had no luck, it's gotta be seized or rusted all the way down. There's an access hole in the brake pedal itself which I stuck a long flat tip thru and into the lip, all it seemed to do was damage the lip on the top of the plunger. I'm not 100% sure but it looks like the brake pedal is actually part of the valve, does that sound right? What can I expect to shell out for a replacement?