Portland drivers may wonder where the air in a vehicle's passenger compartment comes from. Well, as your engine starts to warm up, it also warms the coolant/antifreeze that circulates around the engine and through the radiator. There is also a hose that carries coolant/antifreeze from the engine to the heater core and another that takes it back into the engine. The heater core looks like a little radiator and lives in the air blend box behind the dashboard.
When you turn on the heat, air blows over the heater core, is warmed, and comes into the cabin. Some vehicles have a heater valve that moves coolant through the heater core when the heat is on and bypasses the heater core when the heat is off. In other vehicles, the temperature of the air is controlled within the air blend box by how much air is directed over the heater core.
The engine cooling system, in a larger sense, also encompasses the heater core. Things that adversely affect, say, your radiator will also harm your heater core. The coolant/antifreeze contains corrosion inhibitors that coat the surfaces inside the cooling system, including the heater core. When the corrosion inhibitors are depleted, the cooling system can become corroded, filled with contaminants and may even start to leak.
There are several signs that warn of a leaky heater core: First you may a sweet smell from your vents. This is coolant leaking out and getting into the air. You may even see vapor coming out the vents and notice a film building up inside the windows. Of course, breathing coolant vapors is bad for you.
You may also see coolant on the driveway. Depending on the design of your vehicle, you may even get coolant leaking out into the foot wells of the cabin.
Coolant/antifreeze leaking out through the heater core means that the overall coolant level in the system will be low and the engine is in danger of overheating – which is the cause of mechanical breakdown.
The good news is that the things you do to protect your cooling system also protect your heater core. Changing your coolant/antifreeze as directed by your owner's manual or upon the advice of your Hometown Garage service advisor will help ensure your coolant has enough corrosion inhibitors working to protect this system. Also, quickly repairing any leaks and inspecting hoses for signs of internal breakdown will help keep any from becoming an emergency.
Make sure you consult with your friendly and knowledgeable Hometown Garage service advisor about when your cooling system should be serviced.