I just went through a similar situation. I lost the rear brakes on my 88 runner. Master cylinder was bypassing on the seal for the rear circuit. I never lost a drop of fluid out of the master cylinder. One day fine, the next day no rear brakes, and very spongy pedal. Rebuild/replace the master cylinder.

Yeah, that's kind of the conclusion I came to. Thanks for the help :>) I went out yesterday and bought a new M/C. I'm getting ready to bench bleed it and do the install. Thought I'd check the board here before I got my hands dirty. I'll keep y'all posted on the progress.

Yesterday I went to test drive for the brakes after a bleeding session. When I popped the hood after I got back I had oil all over the engine compartment. The valve cover was making a "sucking chest wound" sound! I had blown a valve cover gasket over the exhaust manifold...Hah! Sooo, I'll be replacing that as well today....gotta love vacation time <img src="/forums/images/graemlins/kewl.gif" alt="" />

Ok guys, that was it. I replaced the M/C and all is well in the brake dept. I also replaced the valve cover gasket and changed the oil and filter while I was at it. Man I love these Toyota's! Everything is so easy to get to on the 1st Gen trucks. I really appreciate all the suggestions I got. Thanks again. <img src="/forums/images/graemlins/cheers.gif" alt="" />