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Smelling antifreeze when I run heat

I smell antifreeze when I run my heat and/or defroster....but BOTH still WORK fine! There is no leaking of coolant into the cab of the car or through defroster vents. It's a 1995 Isuzu Rodeo with 155K miles on it


  • edited January 2011

    Have you checked the level of coolant in the radiator?
    If it has dropped, replenish it and then check it again in a day or two.

    Is there an oily film on the inside of any of the windows?

    If your coolant level drops, and if you have any oily residue on the inside of the windows, then it is fairly evident that you have a leaking heater core.

    There is also a possibility that there is a small leak or seepage under the hood, and that the smell is being pulled into the cab when you run the HVAC system. Have you checked for the telltale signs of a coolant leak under the hood?

    If there is no leak under the hood, then it would appear that you have a bad heater core. Start saving your $$ for this possibility, as the labor costs can be very high for this repair job. If it is a leaking heater core, don't defer the repair for very long, as aerosolized coolant is a very nasty and toxic substance to breathe.

  • edited January 2011
    A leaking heater core is the most likely cause. On this model, the labor to remove and install can be very high. Replacing the A/C core, for instance is about 10 hours labor, since the whole dash has to come out. It seems they built the car around that core.
  • edited January 2011
    I too agree that the heater core is probably leaking. Don't breathe the fumes very long as they are very toxic especially to small children. I would avoid running the heat for this reason.
  • edited January 2011
    I filled up the antifreeze and it dropped maybe one-half inch. There is NO residue on the windshield or windows, and no leaking antifreeze through the floor heating vents. And the thermostat appears to be working fine. But the engine smells like burning antifreeze if I use the heat but there is no overheating or leakage of antifreeze....

    I'm really confused as to what it could be.
  • edited January 2011
    Try a can of radiator sealer and see if that improves things before you rip the car apart..The smell will linger for a while..
  • edited January 2011
    THANKS! I did that yesterday and the antifreeze levels are the same. I drove 50 miles this morning, used the heat and the defrost (both working HOT)...there was a faint smell of antifreeze in the cab BUT the engine smelled like burning antifreeze (the temp of the car went from cold to the proper range - the middle...)
  • edited January 2011

    This sounds like a very small leak...You'll smell it long before you and you see visible signs of it leaking.
  • edited January 2011
    I'm beginning to think you are correct. FOR Clarification: a small leak in the Heater Core? Or a small leak in the Radiator? AND, can I use the heat/defroster without damaging the car-car?
  • edited January 2011

    It's going to be a small leak in the heater core. I doubt you'd be able to smell anything if it was the radiator.

    As long as you keep proper radiator levels there shouldn't be any harm. The problem is it is leaking and it may get worse. You need to get this fixed. There are some stop-leak products that actually work very well.
  • edited January 2011
    OP are you saying that you smell it stronger under the hood than in the car?
    If so, the leak is probably not the heater core and the smell is being pulled into the car by the heater blower.
    Either way, I'd want to have the leak found and fixed. These fumes aren't good for you. If you have pets and they find any antifreeze puddles, it will likely be fatal for them.
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