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. A6 (4F2, C6)
2. A6 Saloon (4F2, C6)
3. A6 / S6 (4F2, C6)
4. A6 Avant (4F5, C6)
5. A4 (8K2, B8)
6. A4 Saloon (8K2, B8)
7. A4 / S4 (8K2, B8)
8. A4 Avant (8K5, B8)
9. Q5 (8RB)
10. Q5 SUV (8RB)
11. A5 (8T3)
12. A5 / S5 (8T3)
13. EXEO (3R2)
14. EXEO ST (3R5)
15. A5 Sportback (8TA)
16. A5 / S5 Sportback (8TA)
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The principle of the thermostat work

The classic TOPRAN 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.