Nissan Repair: low brake pedal, rear shoes, wheel cylinder

Question
I own a 1987 Nissan Multi Automatic 2WD with 192,500 KM. I just replaced one rear left brake line (short steel one from wheel cylinder to flex hose) and long main line to right rear wheel. Then bled system and all seemed fine until the drive home when within 5-10 minutes the pedal got firmer and the brakes were tightening up with each application. It got to the point were the car could not go anymore and brakes started to smell. I pulled over and released the push rod a little that is bolted to my pedal and goes through the booster then the master cylinder. All released and the pedal went soft, pretty much to the floor. Next day I found the rear right wheel cylinder was seized at one end so it was replaced as well as the rear shoes. Bled again in proper order with no improvement in pedal feel or height. Lots of clear fluid at all wheels while bleeding and I am not losing any fluid. Could the fact that the pedal has never been so low that when I pumped it to bleed the system the piston was pushed onto an area of the inner part of the master which may have had corrosion, thus damaging the seal and now I have an internal by-pass/leak. When I say pedal never that low I mean I have never had the need to pump the pedal to the floor to bleed it. When I pump the pedal it gets much better. Am I looking at a master cylinder or master rebiuld? Thanks for any help you can offer.....Louis

Answer
You got it on the master cylinder and going into the corrosion area that has not been into before.  Change the master cylinder and make sure you have the required free play on that rod.  I did that to an old Corvette and burnt all the brakes up.  Check to make sure the brakes are not applying when the car is running and the brake pedal is not pressed.  Also, if you can get it use Ford High Performance Brake Fluid as it is normal fluid but has an incredible boiling point.