Antifreeze Smell Inside My Car With Heater On

heater coreToday I have noticed a slight antifreeze type of smell (kinda sweet) inside my car when I turn on the heater. I have not felt anything different in terms of loss of hot air coming from the vents. What do you think it might be?



Hi there Peter,

I would bet you have a heater core leak, which is located inside the dashboard of the car more so on the passenger side.  Pull back the carpets that are under the dashboard, again on the passenger floor board and feel it with your hands. Does it feel wet, or slick?  If so, the heater core is leaking coolant and dripping it on the floor.

You will need to have the core replaced to solve the problem, which can be very expensive on some vehicles that require dash removal to gain access to the core.

Now, if you are  on a budget, you can have the two individual heater hoses that are leading to the heater core (located under the hood going to the passenger side of the vehicle) spliced together with a cheap plastic hose splice you can buy at your local auto parts store.

This will “by-pass” the heater, you will not have hot air inside the vehicle but you will also not have the coolant leak either.

Here is a video showing the by-pass….sort of, but you get the idea

You can try using a sealer type additive and see if that helps, won’t hurt anything to try it but I have not had much luck sealing heater core leaks with them.  Bar’s leak is a popular additive you can find at any auto parts store and you just add it to the radiator. Worth a try.

I DO like K&W headgasket sealer and I recommend this product everyday to people with internal coolant leaks due to a blown head gasket. Their product is also designed to repair heater core leaks as well…but I have not used it for that situation. You might want to try it yourself, here is the product page


Please share this with your friends,

Austin Davis

Posted in: A/C and Heating

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