Coolant circulation circuit (Mercedes-Benz C-Class W202)

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 heats up, the coolant regulator (thermostat) opens the large coolant circulation circuit. The coolant is directed through the radiator by a constantly running liquid cooling pump. The coolant flows through the radiator from top to bottom and is cooled by the air that blows over the cooling fins.

To regulate air exchange in the radiator, the fan impeller is connected to a hydraulic clutch. When this clutch is disconnected, the fan rotates in accordance with the engine shaft speed, but not faster than 1000 rpm. At a coolant temperature of about 90°C, the bimetallic plate turns on the hydraulic clutch, due to which the fan speed increases in accordance with the engine shaft speed. If the engine speed exceeds approximately 4500 rpm. (4000 rpm for diesel), the fan clutch automatically switches off because the silicone oil inside the clutch becomes too hot. As soon as the engine shaft speed drops below approximately 4500 rpm. (4000 rpm for diesel), the fan turns on again. Due to the intermittent operation of the fan, the useful engine power increases and fuel consumption decreases.

The capacity of the cooling system of a 4-cylinder engine is approximately 8.0 liters, with air conditioning - about 9.0 liters, and for a 6-cylinder engine about 10.0 liters.

The capacity of the cooling system of a 2-liter diesel engine is approximately 8.0 liters (about 9.0 l), for a 2.2L engine approximately 7.0L (about 7.5 l) and for a 2.5 liter engine approximately 7.5 liters. The values in brackets are valid for vehicles equipped with air conditioning.