Did you replace your radiator, or at least take it out and check for leaks? My 01 330i had a mysterious leak like what your describing: low on coolant, no leak. Turned out to be a hairline crack on the upper end cap that was covered by the expansion tank, and didn't show a light because it would only leak out to that point (which is much higher than the sender) and past that only slight pressure/ steam would escape.

Replace your CCV and associated hoses (get a ecs kit and hit the gaskets too!). 200,000 miles is right around the time to open up your wallet to the BMW gods and fix the stuff that should've been replaced at 60 or 100,000 intervals. That said, my 330's radiator was stock, and I'm sure that water pump was in there longer than 60k.

Last thing you want is to be 3 hours away from your own garage and resources and have a incident. Pre failure replacement of wear items is CHEAP insurance if you do your own work!!!

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2006 e53 4.8is Imola / Cremebeige
2005 e53 3.0 Black / Truffle - AT, Sport, Premium, ZCW
2001 e39 M5 Black / Caramel - Extended Leather, Premium Audio