Coolant Circuit Flow

When the engine is running the coolant is circulated around the engine cooling system by the variable coolant pump. From the coolant pump, coolant flows through the cylinder block and the cylinder heads to the coolant outlet connector. Some of the coolant in the cylinder block is diverted through the engine oil cooler before returning to the coolant outlet connector. The primary turbocharger coolant inlet hose is connected to the cylinder block. Some of the coolant from the cylinder block flows through the turbocharger to the Exhaust Gas Recirculation (EGR) cooler outlet hose assembly.

From the coolant outlet connector, the majority of the coolant flows to the thermostat, either directly or via the radiator, depending on the temperature of the coolant and engine speed. The remainder of the coolant flows through the EGR coolers and the heater circuit to the thermostat. From the outlet of the thermostat the coolant flows to the coolant inlet connector on the left side of the cylinder block and back to the coolant pump.

A separate hose from the radiator allows extra-cooled coolant from the radiator to flow through the Automatic Transmission Fluid (ATF) cooler. The coolant from the ATF cooler returns to the system through a connector in the radiator lower hose.

A connection on the upper hose supplies coolant to the auxiliary fuel cooler. The coolant from the auxiliary fuel cooler flows through the fuel cooler and returns to the system through the connector in the radiator lower hose.

The charge air cooling system is operationally independent of the engine cooling system, but connected to it at the radiator upper end tank. When the charge air coolant pump is running, the coolant flows from the pump outlet through the charge air cooler, the charge air radiator and back to the pump inlet connection.

Schematic Diagram - Coolant Circuit Flow