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. A4 (8E2, B6)
2. A4 / S4 (8E2, B6)
3. A6 (4B2, C5)
4. A6 Saloon (4B2, C5)
5. A6 / S6 (4B2, C5)
6. A6 Avant (4B5, C5)
7. A6 / S6 Avant (4B5, C5)
8. A4 Avant (8E5, B6)
9. A4 / S4 Avant (8E5, B6)
10. PASSAT (3B3)
11. PASSAT Saloon (3B3)
12. PASSAT Variant (3B6)
13. PASSAT Estate (3B6)
14. A4 Convertible (8H7, B6, 8HE, B7)
15. A4 / S4 Convertible (8H7, B6, 8HE, B7)
16. A4 (8EC, B7)
17. A4 Saloon (8EC, B7)
18. A4 / S4 (8EC, B7)
19. A4 Avant (8ED, B7)
20. A4 / S4 Avant (8ED, B7)
21. See more in applications

The principle of the thermostat work

The classic FEBI BILSTEIN 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.