How to Tell If Your Heater Core is Going Bad
The heater core acts as a miniature radiator to allow antifreeze to flow through the thermostat to run the heating system. If the heater core is bad, the antifreeze won't pass through it and the heater won't work. It can also cause the antifreeze to leak into the car. Checking the heater core directly is as complex and time-consuming as changing it, since you usually need to remove the dashboard just to reach it. Check for other signs and perform certain tests to see if you have a bad core that needs replacing.
- Difficulty:
- Moderately Easy
Instructions
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1
Check for signs of antifreeze within the car. This includes smelling antifreeze (it has a sweet smell) when running the heater or defroster, or noticing a puddle of antifreeze in the car around the passenger side footwell. This means the antifreeze isn't properly passing through the core and is leaking out.
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2
Look for abnormalities at the vent or defroster ducts. Look for puffs of smoke coming out of either one of these. Check to see if the windshield fogs up while or after running the heater or defroster.
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3
Inspect the radiator and the thermostat. If the thermostat works and the radiator has plenty of fluid but there is no heat, the problem is likely the core.
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4
Get the car warmed up, open the hood and carefully touch the two small hoses running from the engine block to the core. If one hose is cold while the other is warm, the heater core is likely shot.
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5
Flush and refill the cooling system. Open the radiator drain plug (with the car cooled), drain all the antifreeze into a container, dispose of it as per environmental laws and add new antifreeze. Siphon the coolant out of the radiator reservoir and replace it. If the heater still doesn't work, the heater core needs replacing
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Tips & Warnings
You can also loosen the radiator cap after running the engine for about 20 minutes; if antifreeze doesn't squirt out, it is leaking and the problem can be the core. This is very dangerous and not recommended, because if antifreeze does squirt out, it is extremely hot.
