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2002 Jetta with basement smell

My fiance has a 2002 VW Jetta (red) with almost 40,000 miles. About 2 months ago she kept complaining that there was a bad smell comming from the vents whenever she would turn on the car. Naturally I didn’t believe her until I experienced the smell for myself. She said that it started after going to one of the car washes where they do the inside and outside cleaning. I checked under the floor mats and noticed a bit of humidity and they smell was definitely present. Needless to say I removed the floormats and cleaned the carpet of the car and the smell was gone for a week or so. Then I noticed when the weather warmed up a bit (55-60 deg), or after a heavy rain (the car is in Atlanta parked outside) that the smell returned in force.

I went to a dealer and they replaced the sunroof drainage system and cabin filter. For a week or so the smell was gone, but the ambient temperature also dropped into the 30’s-40’s during that time. Last night it rained fairly heavily and the temperature once again climbed up to 55 deg and the smell is very potent when the air is turned on.

I have no idea what is causing the smell and have taken it to a local VW specialist who is at a loss after rechecking the work the dealer had performed (cabin filter and sunroof drain system).

I would greatly appreciate any help or insight with respect to this problem. The car is a blast to drive and is in good condition overall, this is the only real problem we have experienced with it.

Thanks in advance

Victor in Atlanta, GA

Two possibilities.

If the smell is coming from the HVAC vents, then the evaporator drain is clogged and there is moisture trapped in the system, allowing mold to grow. This is fairly easy to fix. Find the drain tube on passenger side firewall, under the hood, and make sure it is clear.

More likely there is water in the padding UNDER the carpet, still there from when the sunroof drains were malfunctioning, and that’s where the mold is growing. The padding holds water like a sponge, and cannot be dried unless you remove it from the vehicle. You’ll have to lift the carpet and feel underneath to see if it’s wet.

Getting to the padding, and removing it, is time-consuming but not impossible. The easiest place to start is the bottom of the door opening. Remove the trim and you’ll have access to the edge of the carpet. My guess is you’ll find quite a bit of moisture under the carpet.

You could have the carpet and padding out of your car in under 4 hrs then either replace or let it dry

If your or your finace’s basement smells like a moldy car, you better do something about that too!

I’ve found that the padding will dry if you hang it somewhere (outdoors in the sun is best) and give it time. I’ve had to do this twice, but not with the same car.