The Stovebolt Site Forums The Shop Area General Truck Talk Here's what I learned about Huck brakes today

If you have a problem with the pressure in the brake system building up over time to the point where it locks one or more brakes (in my case after about 15 to 20 applications), check the compensating port in the master cylinder. It is probably plugged with rust or grit. When this port is clogged, it allows excess pressure to slowly build up the system instead of dumping that excess pressure back to the reservoir. Drill the port out with a pin drill and about a .030" drill bit - the hole is very, very small. Also, after rebuilding the master cylinder, remember to adjust the Hucks for shoe to drum clearance before bleeding the system. If you don't, you'll probably find that you have to pump the pedal twice to build sufficient pressure to stop the truck.

I hope someone in the future finds this post while searching the forums and saves themselves some hair pulling!

Here's a link to help you find the compensating port.

http://chevy.oldcarmanualproject.com/shop/1938/38csm114.html

This is one of those things that was just a way of life in the 50's, because the compensating port was always stopped up, but I'm not so sure I would have remembered it had I not read the post. I still have 2 old GMC's with that type master cylinder.