The Cooling System

To help move cooling air through the radiator when the vehicle is traveling slowly, an electric or engine-driven fan helps out. The whole cooling system is sealed with a cap that traps building pressure inside as the coolant warms. Water boils at a higher temperature when it's under pressure, which explains how you might see a temperature well above 212-degrees F on a calibrated coolant temperature gauge, and still be far from boiling over. If the coolant DOES reach the boiling point, the excess is squirted into a catch tank, where it waits patiently until the engine cools enough to siphon it back into the cooling system.


The coolant system also has another job: transferring engine heat into the car's interior in cold weather. The heater core is essentially a small radiator plumbed into the cooling system that's positioned inside the vehicle's climate control system. So instead of radiating its heat to the outside atmosphere like the main radiator, it transfers its heat to the inside air. By mixing the hot air flowing from the heater core with unheated air, the temperature you feel through the vents can be adjusted. So you get a nice comfortable 72-degrees, which is a bit more pleasant than the 2,000-degree furnace-blast your pistons are feeling. Not to worry, your cooling system is looking out for them.