Cooling System: Description and Operation: Overview

Engine Cooling

OVERVIEW
The pressurized cooling system allows coolant to circulate around the engine and the heater circuit while the thermostat main valve is closed. The primary function of the cooling system is to maintain the engine within an optimum temperature range under changing ambient and engine operating conditions. Secondary functions are to provide automatic transmission fluid cooling, turbocharger cooling and interior cabin heating.
When the engine is running the coolant is circulated around the engine cooling system by the coolant pump. From the coolant pump, coolant flows through the cylinder block and the cylinder heads. Some of the coolant leaving the engine is directed through the turbocharger before returning to the water outlet.
The main engine thermostat is located at the engine inlet up-stream of the water pump. During initial engine warm up the thermostat main valve is closed: preventing coolant flow through the radiator and transmission cooler. When the thermostat main valve is closed, coolant is circulated through the bypass circuit, cabin heater, engine oil cooler and degas tank to allow these systems to function during warm up.
Once the coolant temperature exceeds the thermostat start to open temperature of 82-90°C (180-194°F), the main valve begins to open allowing coolant flow to the radiator system and controlling coolant temperatures as a result. The main valve position is modulated by the wax element to control the engine outlet temperature at approximately 95°C +/- 5°C (203°F +/- 41°F).
In cold climate markets, an optional block heater is available as a dealer fit accessory. The block heater is located in the water pump inlet hose and is connected to a power supply via an external plug.