MTBMaster

As the title suggests, my sunroof is leaking, but the drains are free of debris.

I've a 2004 allroad 4.2L with 69k miles, purchased used back in March 2010. Great car. Great exhaust note. You know the rest...

Took it for its first car wash, drove out of the lot, took a right turn, then feel water dripping onto my left arm. Look up, see the headliner soaked (as well as old water stains I never saw during pre-purchase inspection), with water dripping from the junction of the headliner and A-pillar liner. Turn left, same phenomena in the same place on the right side. A few minutes later, water is dripping from my dome light, from around the OnStar light and moonroof switch! (Fortunately, nothing has shorted out.)

I took some derailleur cable housing from my bicycle repair pile and ran it through the front drains. Nothing. No blockage at all. Can push the cable all the way through to the opening in the door jamb, both sides.

My theory was that through adhesion, water would curl around the top of the roof, between the soft felt-like material on the edge of the sunroof glass and roof, with most of it going through the space between the underside of the roof and the top of the sunroof assembly. This is how I believe it got down into the OnStar console area, and the left and right flanks of the front portion of the headliner. I attempted to fix this by taping a piece of 3/4"-wide rubber weatherstripping, which could act like a curtain and prevent the water from curling underneath and instead dripping down directly onto the gutter tray, and out into and through my debris-free drains.

Car wash today. Wet interior.

What else could it be? My next theory is that the drains from the sunroof tray assembly can only go so far as a solid unit and must pass the water on to some type of hose in which this junction could be faulty? My only problem with this is that the junction would by default have to be below any of the points in the headliner that have gotten wet.

Can anyone shed light on this? My next step is to take down the headliner and proceed from there.

Thank you for reading my first post!

ricam78

Take headliner down. My sunroof tray was cracked where the drain tube connects to the tray. Sometimes the drain tube comes undone, but over time and with a lot of heat it can get brittle and crack. You can either replace the tray or silicone it.

Looks similar to this

MTBMaster

Just read a post on removing the headliner...

Looks like the hose/tray junction could be cracked. Guess it's not as low as I thought--most likely the culprit.

Thanks!

ricam78

Yes, it is a huge PITA. Best of luck to you.

MTBMaster

Any idea on how long it would take, being my first time and solo?!

Does the entire thing have to come off, or can just the front portion be undone and pulled/bent down to access the channels? I'm sure the front drain/hoses are the issue, and not the rear ones.

ricam78

I wish I could help you. This happened to me a while back under warranty and they replaced my entire sunroof tray due to dryrot, so in my care the entire assembly had to come down.

Here is the C5 A6 headliner removal. This should get you 80% done.
https://www.audiworld.com/tech/int67.shtml

MTBMaster

Ahhh yes, that is the step-by-step I found. I was hoping the link you sent was to a 3-step procedure, but it's the same 100-step I came across.

Thanks for the help!

ricam78

Exact reason, I am glad I didnt have to do it!! Best of luck. Go slow and dont fret when you break a clip or 2 or 3 or 4.....as no one is perfect!

MTBMaster

Great.

It's officially rain season now in NorCal, so I need to get this fixed. Fortunately, the car is garaged. However, the leaks have only happened after a trip through the car wash.

MTBMaster

After going through the car wash yet again and finding out my fix didn't work, I have another crazy idea to fix this moonroof leak without dropping the headliner:

-What if I run some plastic tubing through the current drain holes?

I am going to put a fitting+delrin at the tray opening, then secure it with silicone. My only concern is that the opening might not be flush with the bottom of the tray; it might be slightly above the waterline due to the layer of silicone around the delrin. I suppose that would be better than having it spill into my headliner and onto the dome light/OnStar/moonroof switch assembly, as well as the A-pillar/headliner junction.

Thoughts? Just remember that this is all based on theory, not practice, as I have never physically seen or worked on anything in this area.