How determine a thermostat issue
 

I need to determine if I have a thermostat issue in my 2004 X3 2.5i. On a typical cold winter day here in Quebec Canada, with a warm engine, and driving at city speeds, my temperature gauge will indicate a normal "middle " warm reading, and I will get warm air inside the car. If I then drive on the highway, the gauge will wind up in the blue lower area, and I will hardly get any heat in the car. Is this the classic symptom of a bad thermostat?

The BMW TIS seems to indicate that this is a simple enough part to replace. Is draining the coolant really necessary since the thermostat+housing seem to sit high on the engine block?

Thanks for sharing your experiences and comments.

Sounds like the thermostat, if this is your GF's 04 you probably need to change the antifreeze anyway, but no you don't have to drain all of it just a gallon or so.

Here's a link to RealOEM that will show what you're up against.
http://www.realoem.com/bmw/partgrp.d...93&hg=11&fg=35

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