Arrived at this forum by way of doing research for an interior water leak in my '02 A6 Avant. I thought sharing my recent experience might be helpful to the forum. Several articles described the exact same symptoms, an unexplained water build up in rear passenger foot area.

This happened very suddenly and I traced the first noticable instance to a weekend when I hosed the car down for cleaning. San Francisco is very dry during the summer, no rain at all, yet the foot well got wet ?? This was the only explanation.

I read all the artciles about cleaning of drain tubes for the sun roof and also de-installed the battery and holder tray to clean up build-up at the drain plug. I used a small flexible household drain cleaner (about 18" long) to free up dirt in the drain guide itself. Poured water down the drain, water exited below the engine, so no problem there.

However, as soon as I poured water over the windshield, the rear foot area soaked up again. This is a difficult fact to establish, because it takes forever to dry up the interior in order to repeat the test. It's worth trying.

To make a long story short, the problem ended up being a small bulge in the lower rain guard right above the pollen filter intake. Water was seeping through a barely visible crack, into the filter itself, past the air values (if you remove the filter) and into the air duct, then somehow ends up in the rear passenger area.

If you have this problem and can't explain where the leak is coming from, check the lower rain guard by simply pressing firmly against the windshield glass. See if there is any bulge or separation from the glass. I also noticed another bulge in the rain guard on the driver side, where it doesn't matter because water flows directly into the drainage system of the engine compartment and exits though the drain. I must say that Audi engineering should consider a better location for placement of the air intake filter on the passenger side.

I tracked this problem back to a insurance claim for a cracked windshield 6 month earlier. Unfortunately one of this forum site sponsors (Safelite) has performed sloppy work and must not have applied sufficient glue to the rain guard. This is not the first time I have noticed poor craftsmanship because my wife's Subaru had a rain guard come loose after 3 month. Mind you, it is a $600 repair job ($100 deductable with my insurance) ! I managed to get this issue covered under warranty and now Safelite is scheduled to come out and repair the leak.

Hope this helps tracking down the cause of your passengers' wet feet.

 

Thanks for posting! Great explanation of the problem in general and your specific "exception" to the normal root causes.

 

Great detail, thanks for that. I have a similar problem after having an aftermarket radio installed.

 

I know that my 96 Avant has a floor mounted air vent, so Im only guessing that yours does to, maybe the first air tube the water was reaching was the air vent for the floor and that would explain why it was travleing all the way to the back. The vent is mounted under the seat so see if thats where the water is commeing from.