f29pc

Just got a 2004 A6 quatro and sure enough after the first hard rain, wet pass floor. I went to clean out the battery tray drains and found the one under the brake cyl was plugged, the one under the battery was already removed (no rubber drain, just a big hole).
I pulled up the carpet, the TCU was dry as a bone (lucky), and dried out the foam and carpet. I still have the leak and narrowed it down to this.
With the battery out and the tray removed, I put a funnel in the battery tray drain hole, pouring water into the funnel with no water getting in the battery tray, the water is leaking in just below the evaporator drain. I opened everything up but cant see were it is coming through the firewall. The evaporator drain looks dry all the way around, but it is very difficult to see. Is there any way to access the area below the battery tray drains?
ANY suggestions or ideas would be a big help, this is driving me crazy!
Thanks

Redneck Truck

Sounds like the issue I just resolved with mine: crack in caulking between sheet metal body panels that make up the drain channel was letting water in between the panels. When I ran water over the windshield, it would come in right between 2 panels in the floor. Try spraying some foaming glass cleaner over where the water is coming through (the red arrow) and blow compressed air from above until you find the exact source. How about posting a picture of the tray showing where you suspect it's leaking in?

f29pc

Thanks for the reply, it sounds like the same problem.
I used a transmition funnel and lowered the hose through the plentium drain under the battery tray and started pouring water. I kept moving the hose till it stopped leaking in. I have it narrowed down to the pass side near where the upper cat heatshield monuts to the firewall. Below that point there is no water ingress. I had to take off the right front wheel and remove the plastic shield around the control arm to access the area, then used a whole tube of sealant in the area. We will wait for the next rain and see.

Redneck Truck

Don't wait till the next drain to have to pull the carpet up again. Wait for the silicone to dry and perform the same test again. Who knows - maybe you created a place for water to pool and it pours in somewhere else. This isn't one of those things you just walk away hoping it's fixed.

kobe24

Check your AC/evaparator drain. Had issue where all the drains were checked and they were all fine, come to find out my water leak was due to somethign blocking the AC Drain/Evap which caused the water to leak in the rear passenger footwell. It had nothing to do with the Rain.. but I used the defroster was used each time so I chalked it up to rain.