[Ryan Graham]

Brakes can't just all of the sudden "get air" in the lines. Sounds like a bad master cylinder, but older chev trucks had a problem with the abs "dump" valve doing the exact same thing. I'm with you though on not messing with the H3's system. With the traction control and abs and all the other stuff bolted to the master, you may never get it to bleed out properly if you did replace it. If a master cylinder is failing, you can get the pedal to the floor the same way you described and any shop should be able to check the same way you did. Sorry you have such lame mechanics out your way.