The drive of the water pump in a four-cylinder engine is provided by a V-belt, in a six-cylinder engine - by a toothed belt. The way in which the coolant flows through the myriad hoses and channels depends on its temperature at the moment.
- If the engine is not yet warm, then the coolant flows through «small contour», which goes through the engine and the heating heat exchanger. Depending on the engine model, an oil cooler is additionally connected to the small coolant circuit.
- At temperatures above 87°C, the thermostat opens «big outline», in which the radiator is connected.
- If the temperature continues to rise further so that even in the environment of the radiator it reaches 82°C, the viscous coupling of the radiator fan switches to hard direct drive - the fan also rotates.
- Vehicles with electrically driven radiator fan (air conditioner) the fan is connected if the temperature in the radiator reaches approximately 92°C.
Pressurized cooling system
At operating temperature, an increased pressure of 1.2–1.5 bar occurs in the cooling system, which significantly increases the boiling point of water - over 100°C under normal conditions. In this way, a reserve is created, the engine can reach operating temperatures in excess of 100°C, and at the same time there is no «liquid boiling hazard» in the cooling system.
The correct pressure in the cooling system is ensured by the shut-off cap of the expansion tank, which houses the overpressure relief valve (approx. 1.2–1.5 bar) and pressure relief valve (0.06–0.1 bar).
The low pressure valve allows air flow if the coolant temperature drops and therefore takes up less volume.
In a locking cap (1) cooling systems, on the filler pipe (2) The expansion tank contains high and low pressure valves. On the side of the transparent tank there is a marking of the liquid level (3 and 4).
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