Coolant Circuit Flow

Coolant Flow Schematic Diagram 

When the thermostat is fully open, the by-pass circuit is closed and allows maximum coolant flow through the radiator system to provide maximum engine cooling. From the coolant outlet the majority of the coolant is passed through the radiator and the transmission fluid cooler to the coolant pump, with a proportion still passing through the turbocharger, heater core and engine oil cooler.

When the thermostat is open the coolant flow from the radiator bottom hose passes through a venturi. This venturi creates a depression which pulls coolant through the transmission fluid cooler. The upper section of the radiator provides low temperature cooling of the engine coolant for the transmission fluid cooler. In hot climates an additional transmission fluid to air cooler is located in front of the radiator and A/C condenser.

The coolant expansion tank accommodates expansion of coolant due to temperature changes and provides a secondary function to extract air from the coolant. A small proportion of the coolant flow is diverted to the coolant expansion tank through the bleed line connected to the right radiator end tank. This provides a continuous degas function, independent to the thermostat position.