Sometime in the past few years the temp guage changed what it measures
I had this issue on our 2011 528 and learned that somewhere down the line some German genius decided to change what the temp gauge measures. They now measure oil temp, not water temp. I don't know what year this change occurred so you might look into that before you go changing stuff. I know, I know, makes me feel real confident when driving that I am relying on an electronic gauge to tell me if coolant is overheating. By the time that happens you better react quick. Why do they continually tinker with crap that ain't broke. No dip stick, no key etc etc etc.
Ruups, sorry, I had a misspelling in the title!
2006 X3 Silver Grey/Black Lthr/Alum Trim/Sport Prem Pkg/Xenons/Servotronic/Prem Sound/Satellite Radio/Heated Seats/Carbon Fiber Pillars/Blue Tooth/Aux In/Cargo Net/Aluminum Pedals/V1 Hardwired