I have experienced the brake pressure buildup problem a number of times on various vehicles. Shortening the adjustable rod to master cylinder solved the problem in all cases. On a 1977 Ford F150, I installed a rebuilt master cylinder. The brakes built up pressure in less than ten miles of driving. I released a little fluid from the line out of MC and made it home. Shortening the rod adjustment screw about one turn solved the problem.
meansam
