Pic. 4.41. Expansion tank cap check: 1 – a cover of a broad tank; 2 - pump
The cooling system is under pressure. Thus, and also due to the addition of antifreeze, the boiling point of the coolant rises to +126°C. Higher temperatures contribute to more economical engine operation. The excess pressure in the cooling system is approximately 1.4–1.5 bar. If, when the engine is warm, the pressure rises to a higher value, the expansion tank pressure reducing valve in the cap is activated (pic. 4.41). In case of overheating, the fan also turns on.
The motors are equipped with either a viscous fan or an electric fan. These units are switched on by a bimetallic thermal switch if the temperature of the flowing liquid exceeds a certain value. The switch turns off the fan when the coolant temperature drops to a safe level.
Attention! The radiator electric fan can also turn on when the ignition is off due to aerodynamic heating of the engine.
Cooling system components
Water pump. Centrifugal pump that circulates the coolant. On a 4-cylinder engine, the water pump is on the same shaft as the fan. On a 6-cylinder engine, the water pump is mounted on the left side of the engine with 4 bolts.
Radiator. All radiators are made of light alloy. Radiators, like the fan casing, have different dimensions. On vehicles with automatic transmission, a coolant drain valve is installed at the right water reservoir of the radiator.
Thermostat. This temperature-dependent controller controls the coolant circuits.
Circuit at temperatures up to +85°C: the coolant circulates in a small circuit.
Normal operation circuit at temperatures of +85...+100°С: the radiator partially opens; cold coolant from the radiator mixes with warm coolant before it is pumped into the engine.
Maximum cooling at temperatures above +100°C: the thermostat valve is fully open, all the coolant flows through the radiator.
Expansion tank. Releases steam when excess pressure occurs through the pressure reducing valve in the lid.
radiator fan. Depending on the engine, as well as on the equipment of the car, a viscous fan or an electric fan is installed.
Additional fan
If your car is equipped with air conditioning, then two fans connected to each other with a belt are installed in front of the radiator, and the fan located on the left is equipped with an electric motor, from which the right fan also operates.