The thermostat on your vehicle controls the flow of coolant based on temperature. When you just start your engine, the thermostat remains closed to accelerate the warm up process. After a few minutes, it opens up to allow the warm fluid to flow. If your vehicle is overheating but not blowing warm air from the heater, the problem is more than likely your thermostat.

If the thermostat gets stuck closed, it allows no fluid to flow and ends up overheating the coolant already in the engine. If your vehicle is not getting up to temperature when driving, the thermostat is more than likely stuck open. Your engine does not get up to the proper operating temperature where it runs the most efficiently. To fix this problem and get your vehicle's heat restored, replace your thermostat.

This piece from Wahler will restore the proper coolant flow to your vehicle. Designed to fit like a stock unit, your engine will reach operating temperature properly and cool efficiently.

During your thermostat change, fluid loss is inevitable. Be sure to browse the website to get the proper replacement for your vehicle sent directly to your door. Also, be sure to order a new thermostat housing, as the stock plastic units often get broken or warped during removal.

Need a replacement thermostat o-ring? See BMW p/n 11531318402