Thermostat, 80C - E30, E36, E28, E34, E39, E24, E32, Z3, M20, M50, S52

Your engine's thermostat regulates coolant flow and temperature in the cooling system. When open it allows coolant to flow into the radiator to be cooled. When closed the coolant circulates through the engine, where it stays warm. A failed thermostat will either be open or closed with the engine running too cold (poor fuel economy and performance) or too hot (overheating). It can also impact your cabin heating/cooling since that is drawn from your heater core.

BMW used the same design of thermostat for many models from the 1980s-1990s but with different temperature ratings. This is the 80C degree thermostat (in the middle of the temp scale). 80C was standard on E30 325e/325i, E28 528e/535i, E34 525i M20, E34 535i, E24 635CSi, and E32 735i. Thermostats are interchangeable among the models listed below but note that using a non-standard thermostat will alter your engine's performance. On other models this may be a Performance thermostat used with engine fan delete kits.

This is a thermostat made by an OEM thermostat supplier to BMW for this as well many other cooling components. The o-ring seal is included but a housing profile gasket is sold separately.