Last night, while driving home from work, I felt my brakes start to grab. Pulled over into a parking lot and noticed a small amount of smoke coming out of the passenger side front wheel. I let it cool down a bit, accelerated down the parking lot and tried the brakes. They worked but the car pulled to the left while braking. Waited a few more minutes and tried again and this time as I braked the pedal sunk all the way to the floor. Tried pumping it but to no avail, it still sank to the floor.

At this point I figured it was probably the master cylinder and left the car there overnight. However, this morning on my way to work I stopped by the car to check it out. Started it up and pumped the pedal and it felt completely normal.

A little bit of background info: I replace my front rotors and pads last December (about 10k miles ago), bled the system, and everything worked fine. Starting about 4-5 weeks ago on two or three occassions driving home from work the brakes would grab and I noticed the car pulling to the RIGHT while braking (and it seemed the front driver's side wheel was hotter / smelled of brake dust). It seemed to only happen when it was hot out and towards the end of my drive. Each time it did this, once I let the car cool off the brakes worked normally again. I've never had the pedal go all the way to the floor though until last night.

Is it possible that the heat from the brake grabbing boiled some of the fluid, causing erratic braking behaviour? (I'm using DOT4 fluid) It would seem to me that if the master cylinder was good, even if one brake or one half of the system failed, there would still be some resistance in the pedal and thus it would not sink all the way to the floor. Is this a correct assumption?

I still lean towards it being the master cylinder, but would rather not spend the time replacing it if this is not the problem.

Any insight / ideas would be much appreciated, the sooner the better as I'd like to order a new master cylinder today if that's what needs to be replaced. Thanks in advance!