[JLeather]

Ok, not quite sure where to go (although I have my suspicions). It warmed up enough to get some work done on the truck. My buddy came over and attempted to bleed the brakes with me. Started at the right-rear wheel...nothing. A couple drips from gravity, but not an ounce of pressure. Not the biggest surprise ever, given the poor rear brake performance. Went to the right-front...nothing. That was more surprising, given that I drove this truck 30 miles home when I bought it, at speeds up to 55mph. Kept trying the front and started getting huge air bubbles, but no fluid. The more we tried bleeding it the softer the pedal got. Tried the left-front...nothing. Drips, no pressure. Pulled the lines off the m/c and tried bench bleeding it. Plenty of fluid, no issues bench-bleeding. Put the lines back on the m/c and found that suddenly we had plenty of pedal pressure. Started with the front-left and got a nice healthy squirt of clean fluid. Tried it again, got less fluid. Tried it a few more times and back to nothing. Pedal got softer each go-round with the bleeding.

So, I'm suspecting the m/c is bad, but I can't figure out what in it has failed that it will build less pressure each time it's bled. Can't even figure out if the proportioning valve is bad until I've got good m/c pressure. No leaks, system was (and continues to be) full of fluid. So where did all the air come from as we tried bleeding it? It's almost like the more we bleed it the more air that shows up in the system. Like the m/c is sucking in air somewhere, but isn't leaking?