The thermostat is a valve that goes between the engine and the radiator. It's purpose is to keep the engine at the proper operating temperature. When the engine gets too hot, the thermostat opens up and lets the engine coolant flow through the radiator, where it cools off. When the engine is too cool, the thermostat closes and stops the coolant from flowing through the radiator, so the engine heats back up. Coolant thermostat housing assembly regulates the flow of the coolant going through the radiator to keep the engine in its stable operating temperature preventing it from over heating. Therefore, making it a critical component in the vehicle as failure to replace may damage the engine and other critical parts due to overheating which can leave you stranded on the road. This housing also includes sensor for a complete replacement. This Thermostat Fits For the Following Vehicles: 2003-2007 BMW Z4 2.5L 3.0L 3.2L; 2004-2010 BMW X3 2.5L3.0L; 2001-2006 BMW X5 3.0i 3.0L L6; 2001-2005 BMW 330xi 3.0L L6; 2001-2005 330xi Base Sedan 3.0L; 2001-2005 BMW 330i 3.0L L6; 2001-2005 BMW 330Ci 3.0L L6; 1999-2000 BMW 328i 2.8L L6; Fits For the Following Vehicles: 2000 BMW 328Ci 2.8L L6; 2001-2005 325xi 2.5L; 2001-2005 BMW 325Ci 2.5L L6; 2001-2005 BMW 325i 2.5L L6; 1999-2000 323ti Base Hatchback 2.5L; 1999 323is Base Coupe 2.5L; 1999-2000 BMW 323i 2.5L L6; 2000 BMW 323Ci 2.5L L6; Thermostat helps to reduce oil dilution, cylinder bore wear, fuel consumption, exhaust emission, and improve efficiency of the heating system. Customers can find the product you need accurately according to the OE number. OE part number: 1430872; 143-0872; 17111437362; 17 11 1 437 362. Fits For 2001-2005 BMW 320I BASE SEDAN 4-DOOR; 2000-2000 BMW 323CI BASE CONVERTIBLE 2-DOOR; 2000-2000 BMW 323CI BASE COUPE 2-DOOR; 1999-1999 BMW 323I BASE CONVERTIBLE 2-DOOR; 1999-2001 BMW 323I BASE SEDAN 4-DOOR; 2000-2000 BMW 323I BASE WAGON 4-DOOR; 1999-1999 BMW 323IS BASE COUPE 2-DOOR; 1999-2000 BMW 323TI BASE HATCHBACK 2-DOOR; 2001-2005 BMW 325CI BASE CONVERTIBLE 2-DOOR; 2001-2005 BMW 325CI BASE COUPE 2-DOOR; 2001-2005 BMW 325I BASE SEDAN 4-DOOR; 2001-2005 BMW 325I BASE WAGON 4-DOOR; 2001-2005 BMW 325XI BASE SEDAN 4-DOOR; 2001-2005 BMW 325XI BASE WAGON 4-DOOR; 2000-2000 BMW 328CI BASE COUPE 2-DOOR; 1999-1999 BMW 328I BASE CONVERTIBLE 2-DOOR; 1999-2000 BMW 328I BASE SEDAN 4-DOOR; 1999-1999 BMW 328IS BASE COUPE 2-DOOR; 2001-2005 BMW 330CI BASE CONVERTIBLE 2-DOOR; 2001-2005 BMW 330CI BASE COUPE 2-DOOR; 2005-2005 BMW 330CI M CONVERTIBLE 2-DOOR; 2005-2005 BMW 330CI M COUPE 2-DOOR; 2001-2005 BMW 330I BASE SEDAN 4-DOOR; 2005-2005 BMW 330I M SEDAN 4-DOOR; 2001-2005 BMW 330XI BASE SEDAN 4-DOOR; 2004-2006 BMW X3 2.5I SPORT UTILITY 4-DOOR; 2007-2010 BMW X3 2.5SI SPORT UTILITY 4-DOOR; 2004-2006 BMW X3 3.0I SPORT UTILITY 4-DOOR; 2008-2008 BMW X3 3.0I SPORT UTILITY 4-DOOR; 2007-2010 BMW X3 3.0SI SPORT UTILITY 4-DOOR; 2010-2010 BMW X3 XDRIVE28I SPORT UTILITY 4-DOOR; 2009-2010 BMW X3 XDRIVE30I SPORT UTILITY 4-DOOR; 2001-2006 BMW X5 3.0I SPORT UTILITY 4-DOOR; 2003-2006 BMW Z4 2.5I CONVERTIBLE 2-DOOR; 2007-2009 BMW Z4 2.5SI CONVERTIBLE 2-DOOR; 2003-2006 BMW Z4 3.0I CONVERTIBLE 2-DOOR; 2007-2009 BMW Z4 3.0SI CONVERTIBLE 2-DOOR; 2006-2008 BMW Z4 COUPE 3.0SI COUPE 2-DOOR; 2006-2009 BMW Z4 M COUPE COUPE 2-DOOR; 2006-2009 BMW Z4 M ROADSTER CONVERTIBLE 2-DOOR; 2006-2008 BMW Z4 ROADSTER 3.0I CONVERTIBLE 2-DOOR; 2006-2008 BMW Z4 ROADSTER 3.0SI CONVERTIBLE 2-DOOR; 2009-2009 BMW Z4 SDRIVE30I CONVERTIBLE 2-DOOR; 2009-2009 BMW Z4 SDRIVE35I CONVERTIBLE 2-DOOR.