Car Heater Repair: How to Unclog the Heater Core

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  • 1-2 hours
  • Beginner
  • 0-50
What You'll Need

A little knowledge about car heater repair can come in very handy when you're always on the road. If your car fails to generate heat, then you need to check your heater core at once. The heater core is a small radiator like device that coolant flows through to warm car interior. You will inspect the whole heater system.

Step 1 - Check the Coolant Level

The first thing you need is to check the coolant level in the radiator as well as the overflow tank before starting the engine. Low level in the coolant can cause the heater core not to function properly.

Step 2 - Check Leaks

Put equal parts of anti-freeze and water into the radiator and the overflow tank. The first thing you need to notice is if you smell something or see wetness on the passenger side floor. Another thing you need to note is the presence of a greasy mist on the interior of the windshield. This could show that there is a leak in the heater core. If you encounter any of these condition, you will need to replace the heater core.

Step 3 - Set the Temperature

Switch on the engine to set the temperature and leave it in park. Always remember to release the hood latch and keep the parking brake on.

While you are checking the temperature change, locate the temperature gauge (this is located on the dashboard) to see if the temperature is between 190 and 220 degrees. If there are no changes in the temperature gauge, you might have a coolant or thermostat level problem. Take note of the changes while the engine is working.

Step 4 - Check the Radiator

You need to check if the radiator hose is warm. You will have to open the hood and locate the upper radiator hose. Touch it carefully, or if you can wrap your hand in a piece of cloth to avoid any chances of getting burned. The next thing you need to do is to look for the two smaller hoses that connect into the firewall on the passenger side of the car. Take note, this will depend on the model of your car. So if you don’t find the two hoses at the upper radiator, you will have to crawl beneath the vehicle to locate them.

These two hoses are the inlet and the outlet that connect to the heater core. If only one of them is cold or hot, the heater is clogged.

Step 5 - Cool the Engine

Turn off the engine and let it cool down first. Then take your garden hose to wash out the heater core. Then get a clean bucket and place it beneath the hose connections. Use a screwdriver to remove the two hose clamps. Then take again the hose, connect it to the inlet and wash it again. After cleaning, replace the connecting hose and tighten the screws. Add the anti-freeze to the radiator and start the engine again.