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The thermostat regulates the temperature of your coolant. At a predetermined temperature the thermostat will open to let coolant flow to the radiator and be cooled by airflow or the fan. Over time the thermostat will become stuck open or closed, leading to a variety of issues. A closed thermostat will never allow the coolant to reach the radiator and be cooled. Hot coolant will continue to circulate through the engine and absorb even more heat until boiling and the system overheats. An open thermostat is not as bad but is still not ideal - the coolant is always cool, with the temp needle always reading in the cool range. This tells the ECU to richen the fuel mixture to bring the car up to normal operating temp. So your fuel mileage decreases and the car runs rich.
Replacing the thermostat is an easy but messy job. This thermostat includes the main o-ring (but a housing gasket may be required). Consider replacing the housing and any associated temp sensors while you're in there. The cooling system will need to be bled after.
Most of the engines from the mid-1980s through the 1990s use the same thermostat design and they are interchangeable among the different temperatures. This is the 88* thermostat, towards the top of the range. However, keep in mind that BMW spent a lot of time engineering the cooling system to work in all kinds of conditions and changing thermostat temperature is not recommended to fix any failures in the cooling system.
Hailing from Stuttgart, Mahle-Behr specializes in automotive cooling systems. From air conditioning to engine cooling M-B has you covered with OE-quality replacement parts.
This thermostat fits the following BMWs:
1977-1983 E21 BMW 323i
1986-1991 E30 BMW 318is 318ic 325e 325es 325i 325ic 325is 325ix
1992-1999 E36 BMW 318i 318is 318ti 318ic 323is 323ic 325i 325is 325ic 328i 328is 328ic M3
1982-1988 E28 BMW 528e
1986-1988 E28 BMW 535i
1989-1995 E34 BMW 525i 535i
1997-1998 E39 BMW 528i
1986-1989 E24 BMW 635csi
1988-1994 E32 BMW 735i 735il
1997-2000 Z3 BMW Z3 2.8 M Roadster M Coupe
This product was last offered at the strikethrough price on
04-25-2026
This product was last offered at the strikethrough price on
07-08-2026
Don't take chances! Proper maintenance is required to keep your BMW performing at peak levels. The thermostat is important in keeping your vehicle cool, allowing coolant to pass once the engine has reached a certain temperature. Use a high quality thermostat such as this OEM Hella thermostat to ensure reliability and long engine life.
Hella is a premium manufacturer that supplies automotive parts to numerous car brands across the world. Everything from electrical to mechanical genuine parts have been made and supplied directly to BMW before the vehicles ever leave the production floor. Their high quality, long lasting parts have made them a trusted brand chosen to help keep your BMW on the road for many years to come.
As a leading source of high performance BMW parts and accessories since 1993, we at Turner Motorsport are honored to be the go-to supplier for tens of thousands of enthusiasts the world over. With over two decades of parts, service, and racing experience under our belt, we provide only quality performance and replacement parts. All of our performance parts are those we would (and do!) install and run on our own cars, as well as replacement parts that are Genuine BMW or from OEM manufacturers. We only offer parts we know you can trust to perform!
This thermostat fits BMW E28 M5 and E24 M6 with S38 engine.
This item fits the following BMWs:
1987-1988 E28 BMW M5
1987-1989 E24 BMW M6