QUOTE(trfrick @ Jun 25 2011, 09:22 AM)
The MC was replaced about two months prior to the rest of the parts and was working well.
I have plenty of free play/ with the brake pedal until the brakes heat up the it goes away. Shouldn't the excess fluid go back to the reservoir?
Yes, but only if the MC port is uncovered. . . if the port is covered, then the brakes get hot, warm the brake fluid, the fluid expands it has no where to go so it pushed the MC piston back and that takes up all the freeplay. . when the freeplay is gone the ever expanding fluid forces the caliper pistons out and the brakes press even harder on the rotors, they get hotter. . Get the loop your in ?? it just gets worse till the wheel lock up. .
Go back to the "see if you can pry back a pad" thing.
. you should / you want to see the fluid rise in the reservoir . that's the only sure sign the port is uncovered because prying back one pad will also force the other front pads to expand. . . make sure the fluid really is going to the reservoir. .
So the only thing new is the calipers and pads?? So are the calipers direct replacements, or did you do some kind of swap or upgrade ?? If the MC was working fine before, it would seem something is amiss in the wheels. . but both at the same time is questionable. still seems like a MC problem from afar. .
Doesn't your master cylinder have a warning sensor, screwed into the side with a couple of brown wires?? those wires go to the idiot light on the dash i.e. same light as the handbrake warning light. . . that's also the warning light that the piston is not in the middle of the master cylinder on dual circuit master cylinders , hence a problem / leak in the front or rear systems. . .
Another item to look at, If the brakes are getting hot enough to lock the wheels over and over, I gotta think you've got all kinds of air in the calipers by now. .