1968 Brake Question

[Willy 1]

Hi I have been having some issues with the brakes on my car and curious if anyone has had the happen before. Here is the problem. I just finished restoring this car ( 1968 gt/cs) and had all of the brake system apart. Discs on the front drums on the rear. Brakes are set up properly but after driving a few miles the brakes get hot and if I where to try and drive farther it would get to the point that they lock up tight. I changed the brake booster and the master cylinder so I am leaning toward the rod being out of adjustment but would like to rule out any other possible issues. When the brakes are locked up if I loosen the line from the master cylinder to the rear brakes a little oil comes out and the brakes release. Any ideas I know it could be collapsed brake hoses also but would like to figure this out before I start buying a bunch of unneeded parts.
Thanks

 

[speedy02]

Did you have the Proportioning valve rebuilt?

 

[Ruppstang]

Did you replace the rear brake hose? Most likely the proportion valve.

 

[Willy 1]

As of yet I have not done anything. I hate to just start changing stuff doing a trial and error. May have to do it that way though. Think I can rule out anything mechanical as far as the brake shoes or anything like that as when the fluid pressure is released the brakes come off. I never did anything with the portioning valve. Thanks for the reply's