Coolant circuit (BMW 5 Series E34)

The coolant circuit has thermostatic control. While the engine is cold, the coolant circulates only in the cylinder head and in the engine block. When the engine warms up, the thermostat opens the large coolant circulation circuit. In this case, the coolant is supplied to the radiator by a constantly running water pump. The coolant passes through the radiator from top to bottom and is cooled by the oncoming air flow passing between the radiator fins. The fan installed behind the radiator provides sufficient air flow, additionally sucking in the oncoming air flow through the radiator.

The fan contains a viscous coupling. As soon as the air coming from the radiator reaches a temperature of about +82°C, the bimetallic contact engages the fan's viscous coupling. The fan then starts to operate at increased speed and provides increased air flow until the air temperature at the radiator outlet drops to about 460°C. After this, the viscous coupling disengages and reduces the fan's speed.

By intermittently switching the fan on at full speed, the engine's useful power increases and fuel consumption decreases.

[The original material is located on the website: www.bmwman.ru]