Permanently seal sunroof

I have been lurking on Reddit for some time now, but this is my first time posting. Please let me know if any info is missing.

The Sunroof in my 2003 Volvo S40 has been leaking into the headliner and floor mats. I have researched the issue; and unfortunately, the fix in this instance is not as simple as clearing the drain tubes (they are clear and flowing free) or reconnecting the drain tube to the sunroof.

I took my car to an independent Volvo mechanic, and the “proper fix” for this will cost many $$$ and could fail again in the future. He recommended that if I did not care about the sunroof working again, I could permanently seal the sunroof with the liquid urethane such as 3M Window-Weld [link 1 below].

The Sunroof motor has already failed. I can still open and close it with a manual screw under the headliner, so I thought that was not a bad idea. I was planning on putting a bead of urethane on the inner (vertical) lip of the sunroof where the seal around the glass touches the roof. Then close the sunroof so it is flush with the metal. I would then put a second bead of urethane on top of the seam between the sunroof and the metal roof and flatten it down with a putty knife.

My questions are: 1. Do I need to use the primer [link 2 below] that is recommended on the 3M Window-Weld cartridge? If so, do I apply the primer on the roof painted metal, the seal that surrounds the glass of the sunroof or both? 2. I have read that urethane is not UV resistant, but I cannot find information on how fast it will fail with UV exposure. Are we talking weeks/months/years? 3. Is Urethane a good material to stand up to wind (i.e. driving on the interstate)? 4. Do you believe my application steps to be robust? 5. Are there other application methods or materials that you would recommend? I wanted to avoid silicone as I read it can form rust under it.

Links: [1] [2]


I'd probably just throw some of the 3m clear paint protector over the sunroof seams. Clear, water tight, and would be easier to maintain than re-caulking?

There are three main issues with the sun roof that would need to be fixed 1. The track that the sunroof slides in have become miss-aligned and this leads to a small gap between the seal and the metal roof of the car. I guess this is common on this car. 2. There is an inner rubber gasket that sits in-between the roof and the headliner that covers about a 1 inch gap. The gasket has started coming out and expose the gap. This lets water into the headliner. To fix this they would have to remove the windshield and then drop and remove the head liner. 3. The drain tubes pass thru the fire wall via an “L” shaped connector. The tubes have come lose and now drain under the carpet. This unfortunately is also no easy fix as the drain tubes run in frame of the A pillar in my year and not under the A pillar trim like in later years. Thank you for the post and please let me know if you have any other questions.

First off, what is "the proper fix" that your mechanic speaks of? What is the source of the leak if the drain tubes are properly working? Is there damage/dents/missing seal? So the motor is out, you don't care, I see no reason why that would still cause a leak since you can manually close it if the drain tubes are working fine. I'm slightly confused at the situation, really.

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