Once the engine has cooled down, the coolant circulates only in the cylinder head, as well as in the engine block and, if the heating system is open, in the heat exchanger. As the engine warms up, the coolant regulator (thermostat) opens a large coolant circulation circuit. The coolant is directed through the radiator by a permanently operated liquid cooling pump. The coolant flows through the radiator from top to bottom and is cooled by air that blows over the cooling fins.
To regulate the air exchange in the radiator, a fan impeller connected to a hydraulic clutch is connected. When this clutch is disconnected, the fan rotates according to the engine shaft speed, but not faster than 1000 rpm. At a coolant temperature of around 90°C, the bimetallic plate activates the hydraulic clutch, which increases the fan speed in accordance with the engine speed. If the engine speed exceeds approximately 4500 rpm. (4000 rpm diesel), the fan clutch automatically turns off because the silicone oil inside the fan clutch becomes too hot. As soon as the engine speed drops below about 4500 rpm. (4000 rpm diesel), the fan turns on again. The intermittent operation of the fan increases the useful power of the engine and reduces fuel consumption.
The capacity of the cooling system for a 4-cylinder engine is approximately 8.0 liters, with air conditioning it is approximately 9.0 liters, and for a 6-cylinder engine approximately 10.0 liters.
Cooling system capacity for a 2 liter diesel engine approx. 8.0 liters (about 9.0 l), for a 2.2 liter engine approximately 7.0 liters (about 7.5 l) and a 2.5 liter engine has about 7.5 liters. The values in parentheses are valid for vehicles equipped with air conditioning.