I do believe I’ve figured out what goes on with the thermostat failures. Each one occurred within days of an extended idling period (3-4 hours) while commuting home at a crawl during very cold, icy weather. Under these conditions, every bit of engine heat was consumed trying to keep the windshield clear and the interior warm, so the engine thermostat would have been powered to stay closed or nearly closed most of the time. I suspect a higher current flow to the thermostat for that amount of time simply “burned it up”.

The thermostat opens and closes based on coolant temp. It opens and closes even in extreme weather temps. Were you in DFW area when this happened?

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas