Quote:
Not sure what car you're running... but my old 1970 Pontiac Grandprix hit 180F on a bad day... somewhere in there temperature wise you have steam... circulating which is not a good thing...

And nice pun... hot topic!

Your cooling system is pressurized to about 15lbs/in^2, so temps may go beyond 212F easily without boiling.
Hopefully, the system is filled with coolant, which is denser than any vapor, making the circulation of steam impossible (it's all collected at the highest point in the system).
I do note that most thermostats in automobiles are set to open (and release hot coolant to the radiator) at something like 160F-190F (your choice), so my comment about 220F temps is off.
At any rate, I still think the car heater may be the main heat source.

I'm thinking of wrapping my heater ducts with some form of insulation to keep the heat from transferring into the areas behind the dash. The ducts I'm concerned with in my del Sol are easy to get at inside the console, once the cover is removed. Might not be as easy for you in the Bimmer.
Good luck!

/loves teh puns!
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