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How To Replace A Heater Core

A heater core is a small, radiator-like device that regulates your vehicle's interior temperature. However, despite being an integral part of your car’s heating system, it often goes overlooked. Don’t let a faulty heater core leave you out in the cold this winter. Instead, let our handy DIY guide show you how to replace your heater core quickly and easily.  

Here's What You'll Need: 

  • Jack and safety stands
  • Socket set
  • Basic wrench set 
  • Hose disconnect tools depending on application
  • Pliers
  • Drain pan
  • Rags
  • Absorbent/floor dry
  • Hand cleaner
  • Heater core
  • Antifreeze/coolant
  • Distilled water
  • Heater core hoses
  • Hose clamps

Words of Wisdom From The King:

Any time you work on your vehicle, safety should be your number one priority. Keep in mind that the following instructions are not vehicle specific. Be sure you understand the process for your vehicle before you start.

IMPORTANT: Disconnect the negative battery cable before you begin any work on your vehicle.

Steps For Removing Your Heater Core

1. Start by raising and supporting the front of your vehicle. 

IMPORTANT: Always place a safety stand under the raised part of your vehicle. If the vehicle slips off of the jack, it can cause serious injury or death. Check out our previous DIY: Jack Up a Vehicle Safely for more information. 

2. Drain the antifreeze and coolant from your radiator

3. Remove the A/C-heater drain tube from the firewall (if applicable).

4. Loosen the hose clamps on the heater core hoses and remove the hoses if they’re accessible from the engine bay.
NOTE FROM THE KING: There may still be antifreeze in these heater core and hoses. Be sure to have a drain pan ready to catch any extra fluid.

5. After draining the antifreeze, lower the vehicle.

6. Locate the access area for your particular heater core. On most vehicles, the heater core is accessible by removing the plastic panels under the dash. 

IMPORTANT: Be careful not to move the heater core when removing the cover. You could damage it and cause a leak.

7. Once you’ve accessed the heater core, pay attention to its location and how the pipes are positioned.

8. Remove the heater core mounting clamps and any remaining hoses.

9. With rags ready for any accidental spills, remove the heater core.

10. Clean up any spills and, if needed, dry the carpeting with a blow dryer.

11. Check for any seals, O-rings, or other parts that may need to be transferred from the old heater core to the new one.

Steps For Installing a New Heater Core 

1. Transfer any needed parts from the old heater core to the new one.

2. Very carefully place the new heater core in its proper location and reinstall the mounting clamps.

3. Reinstall any hoses that are accessible from inside the car. If possible, do not reinstall the access covers for the heater core at this time.

5. Raise and support the front of your vehicle.

6. Reinstall the heater core hoses you removed earlier.

7. Reinstall the A/C-heater drain tube to the firewall (if applicable).

8. Check the condition of the hoses and replace them if needed. It’s also a good idea to replace your hose clamps any time you’ve taken them off.

9. Close the drain on the radiator and refill it with the proper mixture of antifreeze and distilled water, or use a 50/50 premixed antifreeze. Be sure to follow any instructions in your vehicle owner’s manual for recommended fluids.

10. Lower your vehicle.

11. Check that all hoses are reinstalled, the radiator is filled, and that the radiator cap is closed.

12. Start the car again and let it reach normal operating temperature while checking for any leaks under the car and inside near the heater core.

NOTE FROM THE KING: On some vehicles it’s necessary to “bleed” the air from the cooling system after draining it. 

13. Turn the vehicle heater to high, and then turn on the fan to ensure heat is blowing from the heater core.

14. Once everything is working properly and there are no leaks, reinstall the heater core access covers.

15. Check the radiator level again and top it up if needed.

16. Check to make sure every necessary part has been reinstalled.

17. Dispose of any used fluids in accordance with your local bylaws. Now you can enjoy the warmth of your new heater core!