Why is there a mildew smell in car during rain?

May 19, 2008 2:03 PM

Can someone tell me where a mildew smell in my car might be coming from on rainy days if there are no apparent leaks?

For the last year i have noticed that whenever i step into my car and it's raining there is a strong mildew smell. it happens relatively soon after it starts raining.

the smell lasts for a couple days and it even seems more humid inside the cabin until the smell goes away.

i've checked everywhere inside the car and nothing is ever damp. i've brought it to the dealership and they couldn't find any problems.

has anyone else experienced this?

posted by supertouchme to travel & transportation (13 comments total)

It might be inside the ventilation system.
posted by box at 2:09 PM on May 19, 2008

Have you had the microfilter/cabin air filter changed? My mechanic changes mine every 30k miles.
posted by wongcorgi at 2:11 PM on May 19, 2008

yeah i actually change my filter every 6 months or so. when i run the ac it doesn't smell like mildew.
posted by supertouchme at 2:14 PM on May 19, 2008

Do you have a sunroof?

Because if you do, the sunroof has drains. Little plastic hoses that snake down the a-pillars of the body (they're the metal beams that hold the front windshield and rear windshields in place... and the doors too). The water runs down these into a drain pan, somewhere under the engine. Then the water goes out of this pan out to the ground below. If you have a problem in these hoses or the pan gets clogged, water will start to back up.

This happened to me and all I can say is FIX THIS IMMEDIATELY. Every time it rains it is getting worse. I wound up having to make an insurance claim. Replacing all of those carpets, headliner, and trunk liner ran into the thousand for my VW Jetta. Once mold takes hold, it is basically impossible to get out of your car. It's also (potentially... reviews are mixed) unhealthy.
posted by zpousman at 2:18 PM on May 19, 2008

I had this. It was a leak on the seal between the windshield and its frame (on the upper part near the rearview mirror). It was not readily apparent on my car either - I only realized it when the water actually pooled one time and then came down from that area onto me and the center console while I was driving.
posted by ml98tu at 2:23 PM on May 19, 2008

This used to happen to my car. I hated getting into a humid car the smells like wet sock after it rained outside. It is your ventilation system. I started driving my car with the recycle/recirculate button on unless i specifically wanted air from the outside. That has seemed to cut down on the post-rain mildew/wet sock smell.

I still get the mildew smell if i run the fan after using the A/C. Running the fan on full blast while switching it to suck air from the outside a few minutes will help clear out the smell when you next start your car.
posted by aGee at 2:23 PM on May 19, 2008

When you say that when you run the AC it doesn't smell like mildew, are you implying that when you experience the smell, if you run the AC it goes away? Or, is it that running AC on a dry day releases no smell?

One thing I was going to reccomend was running your AC with the setting on "fresh air" (drawing air from outside - your car might not allow you to set this manually). Then, roll down your windows, step out of the car, and spray some Lysol air freshner, or your choice anti-bacterial air freshner, into the vents under your windshield. This will cause the air freshner to be drawn in through your AC, and will hopefully kill any bacteria built up.

Buuuut, this might not be your problem if you don't smell it with the AC on. Just my $0.02.
posted by xotis at 2:25 PM on May 19, 2008

This wouldn't happen to be a Honda, would it? I've had two Hondas with this problem and my friend now has a Honda with it. In all cases the problem was resolved by turning the "recirculation" button off when done driving the car. That is, you can use recirc while driving, just don't leave it on while parked.
posted by HotToddy at 2:36 PM on May 19, 2008

haha yep. it's a 2002 honda civic
posted by supertouchme at 2:41 PM on May 19, 2008

I used to get that problem in a '96 Civic, and it turned out it was coming from the trunk. I discovered it because the carpety stuff that covered the cardboard that covered the well for the spare tire was damp one day, and when I looked in the spare tire well there was standing water! I never did figure out how the water got in there, but it might be worth peeking back there to see if you've somehow sprung a leak.
posted by vytae at 2:53 PM on May 19, 2008

I had this problem in a Chevy Cavalier. There actually was a leak, but the only way we figured out where it was was by walking around the car spraying different areas with a hose until the person sitting inside reported water coming in.
posted by escabeche at 3:51 PM on May 19, 2008

yeah my car did this after it got flooded once...the rising humidity would make it stinky again. make sure there's no standing water anywhere... ?
posted by hulahulagirl at 8:10 PM on May 19, 2008

The trunk seals were damaged and rain was leaking into my car (Chevy Prizm). I noticed the odd smell first. Then, there was condensation on the inside of the windows sometimes. None of the floors felt wet. The problem was lower than the floor carpet and floor mats, it just wasn't high enough to be felt. While driving, the water worked it's way forward from the trunk, through the backseat, and under the front seats. I never noticed any wetness, pooling, or anything. I never heard water splashing. It puzzled me for weeks, but then my father fussed at me to take it into the dealership. I don't know how they figured it out, but they did.

They completely ripped out all my car's innards to dry out the pools of water under the carpet. They also installed very tiny drains in the tire well of my trunk. I've had no further problems and the smell is gone. It was sad seeing my car innards spread around a garage, though. Luckily, this happened inside of the warranty period.
posted by ick at 10:00 AM on May 23, 2008