Found it.

I stopped at NAPA and got a quart of brake fluid. I hoped it would be enough to fix the brakes on the El Camino. Then I got the idea to vacuum bleed the system. I hooked a piece of fuel tubing to a syringe and the bleed screw on the master cylinder. I got air on top of air. Shouldn't be. Air could be leaking by the bleed screw threads so I sealed then with teflon tape. Still getting air. I reversed the procedure and forced fluid into the system. Then I walked back to get something and noticed a puddle near the left rear tire. The only bleed screw that wouldbn't break loose yesterday. I removed the tire and luckily the brake drum came off easily. Dry as a bone everywhere. Just for grins I figured I would try and vacuum the line to the brake. I got a wrench and a pounder to loosen the bleed screw and found it already loose. Yesterday the wrence must have been real close to a bolt or something and bound up against it and I mistook that as a frozen screw and left it. I put the syringe on the bleeder and vacuumed a ton of air. Then I got the idea to pressure bleed the normal way. I got more tubing and a jar and a length of plastic pipe to use to push teh brake pedal while I controlled the bleed screw. After maybe 10 pumps the fluid came out without bubbles. I tightened the screw and put the brake drum and tire back on. With the engine running I have a nice hard pedal where it should be. A couple hard charges in the driveway to test them and all is well again. I didn't have to use the quart of fluid.