The coolant pump, driven by a V-belt, continuously pumps coolant into the cooling system. When the engine is cold, the thermostat blocks access to the radiator, and the circulation of the coolant is limited by the engine water jacket and heating (see chapter Heating and ventilation).
At normal operating temperature, coolant circulates from the lower fitting of the right radiator reservoir to the water pump and from there to the engine housing and cylinder head. Most then passes through the open thermostat to the top radiator connection, while the other part flows to the heater and, depending on the engine modification, is directed to various parts of the engine, such as the intake manifold and expansion tank or preheater (diesel). In the radiator, the coolant flows through thin tubes connected by cooling vertical plates and is cooled by the air passing through the radiator.