Drum Brake Problems

[Wlee56]

I have a 1969 C-20 Longhorn with manual drum brakes and recently the pedal became very hard & had little to no travel. The brakes will not lock up and when you give the pedal all you can, fluid forces out the master cylinder cap.

I have replaced the proportioning valve and the short lines from the master, along with the front rubber lines and the rear rubber line. All 4 drums have been turned and new shoes have been installed. One wheel cylinder was leaking, so it was replaced. The system was bled and the problem still exists.

I'm thinking it must be the master cylinder as the lines flowed when we bled the system and didn't appear to be blocked.

Anyone have any thought on what this problem may be?