ok so another update, I bled the brakes with the valve correct as hypoid said. (I found that in my haynes after you mentioned it; never heard of anything like that before) Anyway brakes are still a little stiff. I can rotate them by hand, but it takes me pushing and pulling for all I've got on the wheel studs. I'm still thinking master cylinder.

 

when I crack the master cylinder and let some of the pressure off, I can rotate the rotor with one hand on the wheel stud, I think this is because the pads are still rubbing, but who knows. I'm gonna see if I van get the master cylinder in and see if it makes any difference.

 

When you remove the old master cylinder, check the condition of the firewall where it mounts to the master cylinder (check for cracks). Also check the condition of the brake pedal and brake pedal assembly for any wear and verify smooth pedal travel.

Verify the rear brakes are adjusted.

 

thanks 75, the firewall looked to be i good shape when i looked at it. Not much rust, mainly surface rust, and the whole system looked to be in pretty good shape. The asembly that connects the pedal to the master cylinder had rusted and fallen apart inside the master cylinder housing, it think it was just that clip that holds the pedal shaft inside the master cylinder housing. The crappy news is once I replaced the master cylinder it didn't do a thing for the calipers. They are still stuck as can be.

I'm thinking the check valve now, which a buddy of mine says proportions pressure between the two sides of the vehicle. This could easily be the reason for the whole mess, as it was pulling to one side when I hit the breaks for quite a while before this problem. I thought it was just air in the lines. If this dosen't fix it I'm all out of ideas though.

 

The proportioning valve does not regulate pressure from side to side. It regulates pressure between front and rear.

It may, however, still be the problem given that you reported that both sides are locking up.

You never really said if the calipers were free floating. You agreed that I got the design description, but do the move freely?

I know you said the calipers were replaced or rebuilt, but the boot on the calipers piston is supposed to help pull the piston back into the caliper when the brake pedal is released. Are you sure the pistons move in and out freely? I always test this by hand with compressed air. Once the piston is installed and straight in the cylinder, you can do the following test. Put a block of wood between the piston and the other side of the caliper - so when you pressurize the caliper with air the piston doesn't shoot out of the cylinder. Pressurize the caliper with compressed air with the bleeder screw closed - put the air in at the opening for the brake line. The piston should freely (and quickly) move toward the wood block. When you release the air pressure, the piston should suck back into the cylinder slightly (the rubber boot on the piston does this work), and you should be able to push the piston completely into the cylinder by hand. If it ***** in the cylinder, you'll need a C-clamp to push it in. If this doesn't work really smoothly and easily, something is wrong in the caliper. There is an o-ring in the cylinder to seal the brake fluid in, and the rubber boot on the piston to caliper. Perhaps these are the wrong ones - not unheard of at the parts counters in my town.

Good luck

 

thanks for the info tinkerer. Since I already have the new ones on the truck I'm gonna try the proportioning valve first, though.

I didn't know that's what free floating meant, I thought you were talking about the way that they were attached to the truck. (dunce cap for me) The compressed air test seems like a really good idea if this valve dosen't work. I think you're right that it could be a bad rebuild, but the thing steering me away from that idea is both sides being locked up. I'm gonna try the valve first and see how it goes from there. Had to mail order it so we're talking three days from now.