E46 Sticking front brake calipers
Many thanks for your reply! I've been reading many threads on this site to get some ideas, and I'm also inclined to believe the master cylinder is malfunctioning. I can rule out warping because it rolls smoothly once the caliper releases, and I've isolated the problem as being on one side by comparing the relative amount of heat coming off of the rotors after I've driven. I can also feel the wheel binding and hear it resist turning when I start very gradually (no gas, gradual clutch release). The good news is that it goes to my regular mechanic in the morning, so this will give me an area of conversation to begin with.
I'll post my results when it comes back from the shop.