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:  http://www.amazon.com/3M-08609-Window-Weld-Urethane-Cartridge/dp/B000FW61EW/ref=pd_sim_auto_1?ie=UTF8&refRID=1KSQWWJS32CM6T0PYJFQ  http://www.amazon.com/gp/product/B00473W5V8/ref=gno_cart_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER