Does it look like the valve described on my web site?
http://www.musclecarresearch.com/197...-valve-autopsy
If so, there are three o-ring seals in the valve that can degrade over time. They're made of a special EPDM rubber compound that's compatible with brake fluid. The o-rings you can pick up at your local parts store aren't a good replacement because they're usually made of nitrile/buna-n rubber that isn't compatible with brake fluid.
I'm currently looking at the possibility of producing a rebuild kit for valves like the one pictured on my site. I'd appreciate your feedback in this thread if you think it's a worthwhile project:
https://www.yenko.net/ubbthreads/ubbt...;Number=453720