Coolant Circuit Flow

When the engine is running, the engine coolant is circulated around the engine cooling system by the coolant pump. From the coolant pump, engine coolant flows through the cylinder heads and the oil cooler into the cylinder block and the heater manifold.

In the cylinder block, the engine coolant flows forward to the engine coolant outlet tube. When the engine coolant is cold, the electric thermostat is closed and the engine coolant flows direct from the engine coolant outlet tube back to the coolant pump. When the engine coolant reaches operating temperature the electric thermostat begins to open, to control system temperature. As a result, the engine coolant flows from the outlet tube to the coolant pump through the radiator. When the electric thermostat is open, the engine coolant flow through the radiator. This also generates a engine coolant flow through the Automatic Transmission Fluid (ATF) cooler.

From the heater manifold the engine coolant flows through the throttle body and the heater core. These are parallel circuits that are unaffected by the position of the electric thermostat. From the throttle body, the engine coolant merges with engine coolant from the coolant pump and the outlet tube. Afterwards, it flows to the coolant expansion tank. From the heater core, the engine coolant flows back to the inlet connection of the coolant pump.

Expansion and contraction of the engine coolant is accommodated by an air space in the coolant expansion tank and the compliance of the flexible hoses.

The supercharger cooling system also uses the engine cooling system for charge air cooling. For additional information, refer to: SUPERCHARGER COOLING