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Antifreeze smell coming out of vents when i run the AC

My airconditioning smells like antifreeze?

I have a 96 Mercedes C220. An antifreeze smell comes out of the vents when i run my air conditioning , its very intoxicating. what do you think is causing it and how much to fix? the smell goes away when i turn off the ac. thanks

Your heater core is leaking. Get it replaced.

Agree! This is the classic leaking heater core problem. As suggested, get it replaced; these things are not worth fixing. Most of the repair cost will likley be labor. On a rear drive US car the cost is about $250; on a Mercedes I would guess $600+.

Here is a cheap fix. My brother just bought a used 1 ton van for his plumbing company. It had an auxilliary heater in the back which he removed because it was in the way. Search wrecking yards and you can probably find such a heater at a very low cost. Mount it on the passenger side and run the hoses that originally went to the internal heater core to this unit. Next, go to an auto parts store and get a fan that mounts on the steering column. Point it at the windshield and you have a defroster. This was the heating a defrosting system for many cars in the 1930’s and 1940’s.

If this $50 solution isn’t acceptable, you’ll have to pay the big dollars to change the heater core. There were certain advantages including ease of repair to the way cars did things in the 1930’s and 1940’s. Changing out a heater core was no big deal. Now it can be a day’s work.

can you explain to me what a heater core has to do with the air conditioning. I am not running the heater so why should i need a heater core?

Even when “air conditioning”, the air (at least some of it) passes through the heater core.

Your coolant is always circulation through the heater core, even when the heater is OFF, there is some leakage. This smelly stuff comes throught the defroster vents as well as the heater ducts, but with the A/C on, it is diluted! The heat and cold air come into the cabin through the same ducts.

ALL CARS sold in the US have heater cores. I lived in the Tropics for 5 years and actually had a locally made car with NO HEATER CORE, since the lowest temperature was 20C or 68F!

Heater core is like a mini radiator that’s used to HEAT the cabin of your car during the winter. Yes you are NOT running the heater…however water/antifreeze is still circulating through it. When you turn the heat on a door opens up that diverts the air over the heater core that will heat the air and pass it through into the cabin. The heater core and AC all share the same air ducts. So if the core is leaking you’ll smell it inside the cabin.

Get this fixed pronto. If it’s leaking enough you’ll notice the radiator to be low. It could also dump the fluid onto the carpet and floor of the car which then has to be cleaned up.

PS…Don’t do the $50 solution mentioned above. It’s NOT worth it.

Yes, here in Mexico those old Beetles never have any sort of heater. I have gone on trips with someone and it rains, and they give me an old rag to reach across and keep the inside of the windshield scraped off so he can see to drive. By memory, the early Bugs had an engine heater, but they also don’t seem to have them here, but the ones I ride in are older models.

This is clearly a classic example of a leaking heater core. I experienced this on my '86 Taurus, and the cost to repair it (circa 1990) was over $600.00, with the vast majority of that cost being the labor necessary to access that relatively cheap part.

In addition to the odor being “intoxicating”, I can tell you from personal experience that breathing those aerosolized fumes for a couple of months led to some fairly serious lung problems for me. Believe me–deferring this is not good for your health or for the health of your passengers. Have the heater core replaced a.s.a.p. if you value your health.

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PS…Don’t do the $50 solution mentioned above. It’s NOT worth it.

Actually, the $50 solution might work better on a Mercedes Benz than many other cars. Here is why:

Back in the 1930’s, an engineer, Nils Eric Wahlberg at Nash motor company did extensive wind tunnel tests. He found that when a car was in motion, the pressure inside the car was less than the pressure outside the car. With all the ways that cold air could infiltrate the cabin, he devised the fresh air heater that brought in air from the outside rather than reheat the air in the cabin and recirculate it. Bringing in the fresh air pressurized the cabin. This system became the Nash Weather Eye heating and ventilating system which Consumer Reports said when comparing the Nash Weather Eye to the old system was like comparing a modern forced air furnace to a coal heating stove. Eventually, all cars adopted the fresh air system. The last car that I remember using a recirculating heater was the 1957-8 Studebaker Scotsman. Studebaker wanted to keep things simple on this car. Since the Mercedes Benz has a better fitting body than many other cars, the $50 solution would probably work. It would, however, look like hell.

As far as a fan to defrost the windshield, I have a slant back 1978 Oldsmobile Cutlass Salon. It didn’t come with a rear window defroster. I tried a kit where a grid of wires is cemented onto the window but it didn’t hold up. I finally mounted a small fan on the package shelf and it defrosts the rear window very well. The same solution would work for defrosting the windshield as well. In this old Oldsmobile, the heater core replacement was much simpler than my $50 solution. The heater core and air conditioning evaporator are in a box under the hood. The heater core replacement was a 30 minute job. Once in a while, General Motors does do something right.

Hi VDCdriver,

I think I’ve been inhaling these fumes for quite a while now in my 2001 jeep cherokee.
There is not much info online about inhaling ethylene glycol but I’m curious - did you get muscle twitches along with your lung damage? Hope your lungs are okay!

@Monica_K. Quit driving your Jeep until you get your heater core replaced. Ethylene glycol fumes are toxic