Heating System The heater in your car is basically a smaller version of your cooling systems radiator. Hot engine coolant is circulated through a small radiator, often times called a heater core. A fan is positioned in front of the heater core to blow cold outside air over the fins. As this air travels over the heater core, it heats up and becomes the hot air which blows out your heater vents. Like your engines cooling system radiator, the heater core can suffer some of the same issues. If the heater core becomes clogged with rust or sludge, you will no longer have heat. Also leaks can cause a cabin full of white steam and really mess up your windows. If you smell the sweet aroma of coolant when your heater is on, chances are, you have a small leak in the heater core. Often times the heater core is buried under the dashboard, and replacing it, is a major job.