General description (Opel Omega A)

The cooling system includes: a downdraft radiator, a belt-driven heat-viscous cooling fan, a toothed belt, a water pump, a thermostat, and an expansion tank. The expansion tank can be built into the radiator or mounted on the right side of the engine compartment.

The system works as follows. Cold water from the water pump is pumped through the cylinder block and head, then through a bypass hose back to the side inlet of the water pump. Additional circulation occurs through the heater matrix. When the engine warms up to a certain temperature, the thermostat begins to open and coolant is directed to the radiator to provide additional cooling. The thermo-viscous cooling fan is controlled by the air temperature behind the radiator. When a certain temperature is reached, an internal valve opens and the hydraulic drive system rotates the fan blades. As the temperature decreases, the drive is reduced. The fan only runs when required and, compared to direct drive fans, the result is improved fuel economy, reduced drive belt wear and reduced fan noise.