Master Cylinder Problem?

[rrtr996tt]

I would welcome opinions on my recurrent brake problem. I experienced a vibration issue and ultimately fade toward the end of one of my track sessions. I took the car to my dealer and they diagnosed "warped rotors" (I suspected pad deposits) and replaced the front pads and rotors under warranty. The car seemed fine on street driving.
Before my next track day I swapped up the factor pads with Hawk HT 10 track pads, bedding them in as recommended. The car was ok first session, the vibration appeared during the next, and got more severe toward the end. Pulling into the pits, the pedal went to the floor. Upon inspection the driver's right front rotor was scored and was much hotter than the others.

In talking to some of the instructors, the prevailing theory was a sticky right front caliper, perhaps overheating and damaging the rotor and thus boiling the brake fluid. It was at that point I decided to upgrade to the Stop Tech 355 kit (new calipers, lines ect.). The install went smoothly and the brake fluid was replaced as well.

During bedding in, I noticed a grinding noise, pulled the car over and found the right front rotor very hot and my brand new Stop Tech rotor scored.

Has anyone experienced caliper release issues like this?

What other possibilities are there since I've had the same issue on the same wheel with 2 calipers?

[JCtx]

A problem on one wheel doesn't point to the master cylinder. If there's a hardware problem in your braking system, it'd have to be the caliper. The most common problem with SINGLE piston calipers is the sliding pad getting stuck. The pin needs to be cleaned and lubed every once in a while, especially in wet climates. If you remove the pads again, it should be pretty obvious where the problem is by looking at the wear pattern of both pads. And since you boiled the fluid, you need to perform a full bleed job. Good luck.

[VictorH]

He's saying it happened with two different sets of calipers.

[Richbot]

Not sure about the M3's layout but I suspect the ABS system is the only part of the brake system that can mess with one corner at a time, perhaps there is a check valve hanging up in the ABS module?