When a sunroof leaks on any car, the first place to check is usually the drains. Standard sunroof seals are not designed to keep all of the water out, they're designed to keep large quantities out and allow small quantities to pass through into the rain channels and then out of the drain tubes. There are typically 4 drain tubes exiting the sunroof assembly from each of the 4 corners. With the car on level ground and the sunroof open, slowly pour hot water into the channels at either side and watch to see where the water goes. If small puddles appear below the A pillars and B or C pillars, then your drain tubes are working. If not, you may be able to use a speedometer cable to free any clog. Compressed air may blow off the small rubber connections if used improperly so I typically avoid it.
Water drips on the front occupants
For many Audis, the channel for the rear edge of the sunroof is on rails and will slide forward and back with the sunroof as it is opened and closed. A common fault is for the two small arms on either end of the sliding channel to break, and the nylon strap to become disconnected. When this happens, the next time you slide your sunroof back, it pushes the channel into your roof and the mechanism has no way of pulling it forward again when the sunroof is closed. Without this sliding channel in place, water pools into your headliner and drips on your front seat occupants. In this post, I'll detail what you can do to fix the issue.
Tilt your sunroof forward, then using your hands reach behind the accordion piece. It's wedged on the glass side and comes out easily. On the headliner side there is a clip on the rearmost edge that you disengage by pulling towards the center console, and at the front there is another clip that you disengage by pulling the piece towards the rear of the car. Remove this part on the passenger and the drivers side.
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Step 2: On each side of the sunroof panel there are three T-25 Torx screws, 6 screws total. With a paint pen mark the location of the heads prior to removal, so that you can get the glass adjustment right on when reassembling. Remove the front and rear screws, and just loosen the center screws a few turns.
Step 3: Push up on the sunroof glass and the panel will come out, set the panel aside, some place safe.
Step 4: With the sunroof panel out, grab a flashlight and peek back into your roof. You'll most likely see this.
The red arrow points to the nylon strap. Grab a coat hanger or long needle nose pliers to fish it out, then use the nylon strap to pull the channel (blue arrow) out.
Step 5: Here you can see where the arms of the channel cracked. It's identical on both sides. These parts are some kind of pot metal, so welding may not work, and the fracture point is so small that adhesive may not work either. You can try wrapping with something else, but your best bet is to replace the part entirely. For my Audi S8, the part number is 4D0877445D and it's item 14 in the diagram below. FCP Euro does not normally stock this part, but we have access to just about anything, so armed with the part number you can send us an email or request the part on our website. Audi used the same channel in a few models, and yet others have a similar channel but different part number. Make sure you get the right piece. To remove the channel, unscrew the cap on the channel pivot, either side, and slide the "foot" out of the "groove" The rest is fairly straightforward.
For a temporary solution, you can manually slide the channel so that it aligns with the rear edge of the sunroof opening, then reassemble your sunroof. The channel wont move until you slide your sunroof back. So fingers off the button until you're ready to tear into it again. The sliding channel also is the rear stop for your sunroof sun-shade. If you slide your sunshade too far back it will push the channel back as well.
Assembly is reverse of removal.
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About the Author: Glen Cordle
Glen is a mechanical designer from Minneapolis Minnesota. An old-school motorhead at heart, he respects anything that's had passion poured into it. A jack of all trades, master of some.
