The thermostat is located at the rear of the engine. During heating, a closed thermostat prevents fluid from passing through the radiator. As the engine reaches normal operating temperature, the thermostat opens and allows hot coolant to enter the radiator where it cools before returning to the engine.
In the cooling system at operating temperature there is an excess pressure of 1.2-1.5 bar, which significantly increases the boiling point of the coolant above 100°C. This provides a certain reserve. The engine can be heated to temperatures above 100°C without the risk of liquid boiling in the cooling system. To maintain the correct pressure in the system, the radiator is equipped with a cap with a safety valve (1.2-1.5 bar) and vacuum valve (0.03-0.1 3 bar). The vacuum valve lets in air when the coolant decreases in volume as it cools.
Coolant circuit diagram
1 - coolant pump;
2 - cylinder block;
3 - cylinder head;
4 - thermostat valve;
5 - thermostat;
6 - heater;
7 - radiator.