I have a 2003 a6 that has a re-occuring water leak on the passenger side. About 2 years ago I started to have the issue. The passenger front floorboards would get soaking wet. I could dry it out and the next rain it would be back. I checked and cleaned the drain under the battery and thought the issue was fixed. A couple of weeks later the water was back after the next big rainstorm. I then double checked that drain and also checked my sunroof drains. Everything was clean and flowed well. During this time I had a windshield replaced and found the new one to be leaking. I had the company replace it and the leak went away.

Fast forward 2 years. The leak is back. I have checked the drain under battery and the sunroof drains with no luck. They are clean and flow well. When I watch the car it seems like the water is coming in on the top left edge of the passenger floor compartment. right where the carpet ends and the dash starts there are a few drips. I checked my coolant level just to be safe even thought the water on the floor smells nothing like coolant. I suspected possibly the heater core. But my windshield isn't fogging up and I don't have the teltale smell of coolant inside of the car. Coolant level was just fine.

So I am confused as to where this water is coming from. I put a small flashlight right up into that area and turned off all other lights and looked all over from outside of the car. Nothing there either

I have also checked the passenger compartment air filter. It's right there and could be exposed. From what I can see nothing is coming in there either unless somehow it is running down the windshield and getting in the back of that compartment which seems unlikely as it goes under the body right there.

Where else can I look?

thanks up front for the help

 

You have probably fixed the problem by now, but hey ho.

Take the battery out and find two drain holes (1 inch round approx) under the battery tray / bulkhead. Bodge a screwdriver down them then clean all composting leaves etc.

My car A6 1999 1.8T (yours may be similar) still had this problem after doing this fix, turns out that leaf debris was further up the bulkhead, just under the windscreen between the wiper motor and the bonnet release cable grommet and behind the ECU.
The water was getting in under the ECU unit and dripping down the fuse box bellow it.
This bulkhead area has no drainage at all!
Debris had gathered under the ECU box, and although I have cleaned it off, there is still no way for this to drain other then sloshing about and dripping over the bulkhead (lip / weld) when the car is in motion.

Very bad egg Audi!

 

if your window has been replaced, the cowl at the bottom of the window was never put back on properly. So the water will leak down and through the cabin filter. Fix cowl and you fix your leak