The circulation of the coolant is regulated by a thermostat. When the engine is cold, the coolant circulates only in the crankcase and the heat exchanger of the heating system. When the liquid is heated, the thermostat directs the liquid through the radiator. The circulation of the coolant is carried out by a pump driven by a V-belt. The coolant flows through the radiator from top to bottom and is cooled by the air flow passing through the fins of the radiator, which occurs when the car is moving.
In OHC and V6 engines, the fan speed is controlled by a viscous coupling, the operation of which is controlled by a thermal switch located in the fan motor step. Thus, when the engine crankshaft is rotating, the fan does not operate constantly, but only turns on as needed. The fan speed depends only on the engine temperature and does not depend on the crankshaft speed. In any case, the fan speed cannot exceed the crankshaft speed.
The diesel engine fan is also driven by a V-belt, but it is switched on via an electromagnetic clutch, the operation of which is controlled by a thermal switch.
In the 4-cylinder DOHC engine, additional cooling of the liquid in the radiator is carried out by means of an electric fan. As soon as the temperature of the coolant increases, the thermal switch turns on the electric fan motor via a relay. When the temperature of the coolant decreases, the thermal switch automatically turns off the electric fan motor.
The expansion tank is a container that contains a reserve of coolant. The tank compensates for the change in the volume of coolant when it is heated in the engine and cooled after the engine is stopped. Due to this, the cooling system is always filled with liquid and ensures effective engine cooling. Filling the cooling system with liquid is carried out only through the expansion tank.
Warning: When the engine is stopped and the ignition is on, the electric cooling fan of the 4-cylinder DOHC engine may turn on automatically. Due to the heat build-up in the engine compartment, this may happen repeatedly. Therefore, when working in the engine compartment, you must always be prepared for the fan to turn on unexpectedly. Unless the nature of the work performed in the engine compartment requires it, the ignition must always be off.
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