Had this problem once before. I know the likely culprit, but just in case you think it can't happen............
I drive for 20 minutes in the 242 Ti which has been sitting for about a year in the garage, awaiting new exhaust mani. bolts (and my time).
I have brought along a gallon of water and a spray bottle...really!
Soon after leaving the first stop, the steering wheel begins to vibrate, as I pull onto the interstate, it gets worse, so bad I dare not go over 50, the wheel is moving 1-2 inches at the rim! I think the wheels will come off. Next exit I'm off , step on the brakes, nothing, pedal to floor. Pumping gets something , but have to stop with the emergebncy brake (guess that's what it's for).
Get out, smell of friction material, feel LF wheel, hot!
Get spray bottle , begin spraying caliper and hub. After about 5 minutes, and 16oz. water. Brakes OK, not hard but OK.
Three miles later, wheel vibrating, brakes gone. Another 10 minutes and 32oz. Brakes OK and make it home.
Whew!
I'm goin to look at the caliper, but why the vibration?. DO you think the rotor is warping and then OK when cooled, or does some thing else cause it to vibrate, causing it to hit the pads and overheat?
Is the vibration a symptom, or the cause of the overheating?
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744 & 745 GLE's (IPD a-sbars)16v M46, 245 SE(IPD a-sbars) auto, 242Ti M46(IPD springs and bars), 745GL 8v auto