Thermostat is a device for maintaining a static (constant) temperature, as its name implies. There are thermostats of different designs in many devices and mechanisms, from water heaters to refrigerators. There is also a thermostat in a car's internal combustion engine (liquid-cooled, of course). In a car, the thermostat regulates the temperature of the coolant (antifreeze): it accelerates the warm-up of a cold engine and provides heat removal from the hot one. Therefore, the engine works more efficiently and more comfortably for the driver, especially in winter - without a thermostat, the stove would usually blew cold air.

1. X3 (E83)
2. X3 SAV (E83)
3. 7 (E65, E66, E67)
4. 7 Saloon (E65, E66, E67)
5. 3 Compact (E46)
6. 3 (E46)
7. 3 Saloon (E46)
8. 3 Touring (E46)
9. 3 Coupe (E46)
10. 5 (E60)
11. 5 Saloon (E60)
12. X5 (E53)
13. X5 SAV (E53)
14. 5 Touring (E61)
15. 3 Convertible (E46)
16. 3 (E90)
17. 3 Saloon (E90)
18. 3 Touring (E91)
19. 3 Coupe (E92)
20. 3 Convertible (E93)
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The principle of the thermostat work

The classic HELLA brand Thermostat, coolant is a movable valve that moves due to a change in the external environment - heating or cooling of antifreeze. The thermostat is made of a thermoelement filled with a substance resembling wax in structure - ceresin, with the addition of copper powder, graphite or aluminum for better thermal conductivity. At a certain temperature of the antifreeze, ceresin expands, opening the thermostat valve. When the motor cools down, ceresin contracts and the thermostat closes again.