Clutch won't disengage

I agree with Mark, flush the system with fresh, non synthetic dot4 brake fluid. If that doesn't solve your problem, I would think about replacing the slave cylinder, if that doesn't work, it may be the master cylinder. If you start replacing parts, I would start with the slave as that is an easy fix, the master is no fun and for all but the truly masochistic, requires a helper. I used the synthetic Valvoline brake fluid in my system and I believe it destroyed the seals in my new stock type master or my new long throw stainless slave. I am still wrestling with the problem.
Art

Thanx much. I'll bleed out all the old fluid.