Engine Overheating Even a clogged heater core has the potential to obstruct coolant flow enough to cause overheating. A low coolant level (caused by a leaking heater core) can lead to overheating and possible engine damage.

What to do if your heat pump is blowing cold air

1. Turn off the heat at the thermostat and check your air filter. If it’s dirty, change it!
2. Make sure the thermostat is set to “AUTO”, not “ON”. When set to “ON” the fan will stay on even when your heat pump isn’t actually heating.

It can prevent the heater from blowing out warm air. Unclogging a heater core is often a matter of having access to the correct how-to-do-it information and the right tools at your disposal. Once you have access to the right information and tools, you could fix it just like a professional plumber.

You can still drive on with the condition; however, you should not, for a long time. The heater core uses the engine’s coolant, and a faulty heater core affects the cooling effect which then raises the temperature. Not curing the issue and continue to drive the vehicle this way can lead to further engine damage.

Cabin heat comes from hot coolant, so drive long enough to warm up the engine. If coolant temperature is acceptable, feel both heater hoses, which should be hot.

Start the engine and let it idle for about 20 minutes to bring the engine to operating temperature—when the engine has reached operating temperature, you’ll feel the upper radiator hose getting hot. When you see a stream of coolant free of air bubbles flowing through the clear hose, tighten the screw again.

If you don’t bleed the coolant system you can have air pockets in it. This can cause the gauge to spike and can lead to overheating. The coolant system can self-bleed some between the thermostat and over-flow tank, but to do it properly you should fill the coolant and run the car with the radiator cap off.