UkiahA8L

According to my Audi mechanic, the sunroof does in fact NOT make a tight seal when closed. It was designed to drain water through the A-pillars I believe even when closed and the trouble begins when the drain gets clogged by pine needles and such.

Panelhead

This is the evaporator core drain. There are two, right on the driveshaft tunnel.
I use the basketball inflator needle to blow this out. Just pull back the carpet to access the tubes. Then fight the Audi connector. Mine now have a hose clamp installed.
There are three leaks areas. The evaporator core, sunroof drains, and ones under the hood. All due to the design. I check to see water dripping on both sides for the AC. Vacuum out the two under the hood, and need to service the sunroof SOON. Car sits under a live oak and this was a huge year for pollen. This first year this has plugged.

Davidlorrain

That's my question also!

MP4.2+6.0

It does seal well. Theories otherwise would mean big time air/wind noise at speed. Drains are there variously so if you use tilt position and there was some standing water or dew from the prior storm or night, it runs off it forward and has somewhere to go besides your lap. Or if parked and tilted and it rains or the sprinklers turn on or whatever, it has somewhere to go. Or if seal starts to fail, rain has somewhere to go. Or, ...

Davidlorrain

Thanks for sharing you knowledge! Sometimes it's hard to tell what is right on here! I love this forum saved me money already! Cleaned my own AC drains checked the other 2! Unhooked my noisy deflecter motor! Never new had soft door close till I read a post on it and tried it then smiled!! Bent shade cover when open vent on sunroof is how it works!!

haggisuk

I have found in my experience that the sunroof is not water tight.

The biggest issue I have is where I live is quite dusty and it's not uncommon to find a fine layer of dust/sand on top of the car then when it rains that is carried into the sunroof channel and works it way down the drains.

That fine sediment gathers at the exit point and eventually blocks the drains and requires flushing out to keep them clear.

aTOMic

I'm In!
I recently bought another '04 A8L and the first one was a very early build while the newer sage green one's VIN is about 5000 higher. I had water ingress on the beige(older) one and considered replacing the gasket until I saw it's ~$200 IIRC. Gasket is a misnomer; it is made of mousefur-like material with not much "give", and on my 160k mile car the fur was completely worn off on the contact surfaces, which is essentially the entire perimeter. The fun-to-clean drains are behind the fender liners; I cut the nipples off and vacuumed a bunch of water and the crap that had been clogging them through the fronts. I think some ******** used compressed air to blow them out and caused one or both of the rear ones to detach under/above the headliner, so I bought a piece of vehicle wrap (black) and sealed the roof, and pulled the sunroof fuse until I get around to fixing it because removing the headliner is a big job. The tubes are terribly small, BTW! Why, Audi, why? The newer build uses a much better sealing soft gasket without the mousefur. The wrap looks good in any case, and I'd do the green car (without sealing the sunroof) if it weren't for the relentless Tennessee sun and the almost-silver green reflecting far more heat than black would.
My '98 Passat, which I bought new, had a "campaign" offering a free wash (or some equally useless compensation) to cut the nipples off! I circumcised my fronts, which are in the door jambs and are quite large - about 1 cm compared to the Audi's which are ~5mm IIRC. The rears were hard to get to so I rinse them periodically. The strangest part is there WAS a multimillion dollar class action starting with the '99 models, dammit, and VWAG had to pay to remediate any damage or previous repairs caused by water ingress, from the roof or the cowl, which has another amazingly stupid design: The drain (in front of the firewall), while large, is secreted under the battery, so wet leaves turn into compost and eventually result in a nice compost tea soaking the front footwells and electronics under the floor (did I mention stupid design?).
Why VWAG doesn't learn from its mistakes is beyond me.