Cannot fully bleed brakes

[Taylor Hackel]

I have a 2007 Trailblazer that I cannot get a good brake pedal on. It started with me doing a brake job using a power bleeder where I accidentally ran the master cylinder dry. Removed and bench bled it (and the entire system) and still could not get a good pedal. Since it was cheap I opted to replace the master cylinder, bench bled it, bled it on the car, and re-bled the entire system several times using several different methods (2 man, power bleeding, mityvac, gravity bleeding) but cannot get a solid pedal.

With the engine off the pedal is fairly solid, only sinking a bit when I put my full weight on it. But as soon as I start the engine the pedal sinks to the floor. I’ve got a Tech 2 clone arriving tomorrow to bleed the ABS, but beyond that I’m at a total loss as to what I can do to get my brakes working again.

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