THSCC Forums

AC in my 1998 Honda Civic seems to be working fine (cold air on demand). But when I first start the car in the morning (trip to work) or in the evening (going home), I get a strong odor for about the first 5-10 seconds of operation from the vents of what to me smells like uncured silicon sealant/caulk.

I am assuming that I don’t have something (mold, etc.) growing in the A/C plumbing as it is not a “musty” or “moldy” smell. It has a definite chemical smell to it. I have no idea what refrigerant smells like (if it even has a smell). So I don’t know if this is some weird sign of a slow refrigerant leak. It didn’t always do this. I have noticed it in about the past six months or so.

Currently I have just been rolling down the window when I first start the car to clear out the odor. But I am afraid this is maybe some indication of a problem that I need to look into. Google searches so far is not providing me with any hints.

Any ideas?

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Richard,

Any chance it smells more like "sulfur/rotten eggs"? Does your car have a functioning catalytic convertor? Could the smell be pulled in from the exhaust? Some Cats with some gasoline will make a nasty "rotten egg" smell. Particularly common with Japanese cars I've followed in traffic.

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Dick Rasmussen

FS 50 2018 Mustang GT

I am pretty sure it is not a sulfer smell. The engine, transmission, exhaust is 100% stock (no mods) and as far as I can tell the catalytic convertor is working. The exhaust doesn't have the same odor as what I am getting from the AC vents.

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Richard,

I'll let an AC expert comment but I don't think the AC "freon" has an odor.

I believe the "silicone rubber" smell is acetic acid. See a dictionary for where it is used. Citric acid may smell similar. Lots of sources of both.

Have you tried running the vent fan before starting the engine? I've detected some weird smells from other cars in traffic so "rotten eggs" may not be the only cat smell.

It probably isn't an antifreeze smell from a very slow leak.

Good luck.

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Dick Rasmussen

FS 50 2018 Mustang GT

Yes it does, I have "accidently" released the contents on a couple AC systems. The freon itslef, or R132, may not have an oder but then oil does.

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91 Jetta GLI STS/DSP 111
85 Porsche 944 ASP 11
http://www.blackforestindustries.com

Back when I had my M Roadster I had no place to park it in a protected manner other than a shed beside where my dawgs are kenneled. In fact, part of the kennel was also covered by the same shed with some farm wire fence in between.

I got in it one day to go somewhere and drove around all day with no issues. In the evening when it was time to come home it had gotten chilly so I put the top up and turned on some heat. WHAT IS THAT SMELL??? Man, that smells like...uh...DAWG FOOD!

Seriously strong dawg food odor. Coming from my heater core. Took the car into the dealer and it turned out mice had made nests in the heater core as well as in the tunnel area of the car on top of the transmission. They took pictures (which I probably still have somewhere) of all the crap they took out. Ended up costing me around $1200 to get it demoused. The guys at the dealership got a huge laugh out of that one.

I paid the bill and found a better place to keep the car while things were getting built.

You say it smells "chemical", but I'm just throwing this out as you never know what critters might be packing away for the winter. In my case it was dawg food stolen while the puppies slept (bad puppies!). Ugh.


--Donnie

Adam,

Good to know that AC oil has an odor. What does it smell like? FYI Propane, etc. has "odor" added to it to make leaks easier to detect before "boom" happens.

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Dick Rasmussen

FS 50 2018 Mustang GT

Donnie brings up a good point here. When I bought the Protege from my friend Brad, the blower on level 3 or higher made a sound like popcorn. He thought the blower motor was going. I pulled the blower motor, and found about 5 years worth of ground up dry leaves and tree material like 'helicopter' seed carriers in there. I weighed the stuff after pulling it, and it turned out to be a full 12oz. It was amazing how much better the ventilation system was after cleaning that crap out of there.

The moral is, if you park it under trees or outside a lot, it could be something that is 'collecting' inside. - AB

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'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

If the source of your smell is AC oil your AC would not be blowing cold or will not in the near future. I have recently had to work with some AC oil and I did not remenber the smell being like silicone.

Try this next time put your AC on Recirculate or Max and see if you have the smell. Your car gets its fresh air from under the cowl and something may have fallen in there. At the glass shop I have removed some very disgusting things from the cowl. I have also had to de mouse my ventilation system when I drove freight for a living and parked the datsun at the terminal for a year. And no it did smell like silicone either. The mice made their nests from carpet and leaves.

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George Bright Member # 141
One of the youngest of the old farts.
Yes I voted against you joining the club.

Acetic acid (the solvent for silicone caulk) is just an advanced stage of fermentation (ethanol goes a few more steps to acetic acid). I'd guess you are smelling some sort of fungus/mold doing it's thing.

The first thing I'd do is make sure the drain for the condensate is not blocked.

Scott

Ok, I will check into that (blockage in the drain). When you started talking Acetic Acid, I flashed back to my B&W darkroom days. It might have the same smell as Stop Bath. I think I have just smelled more silicone caulk recently than stop bath.

Thanks everyone for the help.

_________________
Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.