S70 Rusted Sunroof Repair

[N_D]

Just wanted to share my experience attempting to repair my leaking sunroof.
*I do not claim that this is the proper way to do this*

Since I purchased the car a year ago the sunroof had been leaking progressively worse until last month when the headliner began getting wet after rain.

I first removed the sunroof and peeled the gasket off. For those who don't know the S70 has a different style of gasket/sunroof than the 850 (S70 has single piece gasket while 850 is multi-piece). The gasket has a folded metal core in it so I tried not to deform the gasket too much. There are also two plastic shims that serve as a kind of wear plate between the wind deflector and the gasket at the front corners of the sunroof, be careful not to bend and snap them as they become brittle.

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^A cross section of the sunroof gasket.^

After peeling off the gasket I discovered that the metal sunroof frame was severely rusted and had begun to separate from the glass. The glass is bonded to the frame with a very hard rubber like sealant, water seeps under the sunroof gasket and sits in the depressed area of the frame causing it to rust.

To repair this I first scraped/filed off as much loose rust as I could and pried the frame as far away from the glass as I could without breaking anything using wooden wedges and continued to clean as much rust out as possible. I then applied a rust converter to the remaining material.

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Once the rust converter had dried I cleaned off and roughed up the old sealant on the glass with a file to promote adhesion. I then applied a VERY heavy bead of silicone to the frame and clamped the frame and glass together for 24 hours.

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After allowing the silicone to cure fully I trimmed the excess off with a razor blade. I then cleaned any chunks of rust and dirt out of the groove in the gasket itself. When re-installing the gasket I started with one end of the gasket its original position at the back centre of the sunroof and squeezed silicone into the gasket as I pressed it on to the metal frame. When I reached the two plastic shims in the front corners I first squeezed silicone into the gasket, then pressed the shim in, then layered some silicone on top of that before pressing the gasket onto the frame. This was a two person job for me, one holding the gasket while the other applied silicone. I used a rubber mallet to make sure the gasket seated all the way on to the frame.

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Once the gasket was fully installed I lightly clamped down the two ends of the gasket. I used the flange on the metal frame as the other contact point for my clamp so as not to crush the front section of the gasket.

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After letting the silicone cure 24 hours again I trimmed the excess that squeezed out. I did not apply a heavy enough bead in some areas and the silicone did not squeeze all the way through to the top of the sunroof so I filled those areas in afterwards. I believe this is the most important step in resealing as any gap between the top of the gasket and the glass will allow water to seep in and cause the same problems again. Having a completely watertight seal between the gasket, frame, and glass are critical in forcing water around the outside of the gasket into the sunroof drains, rather than into the frame and onto the occupants heads.

Due to the excess amount of space being taken up by all the extra silicone behind the gasket there ended up being a small gap between the two ends. This could probably just be filled in with silicone if some time was taken to mold it properly but I instead went to a wrecking yard and got a short section of gasket and cut the proper thickness to fit the gap with a band saw.

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Once all was said and done there was a considerable mess left on the glass by silicone smears. These are a pain to remove but can be helped by using a silicone removing gel and gently scraping with a razor and rubbing with a paper towel.

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Sunroof is now reinstalled pending some adjustment and cleaning but has weathered its first rainstorm successfully.

[Ozark Lee]

Nicely done. I'm going to guess that you do a fair amount of woodworking, you have a collection of clamps that rivals mine.

...Lee

[hausmeister]

That is also on my to-do list for the 850. Is removing the glass panel from the assembly much work?
Also I am kind of dreading all the rust that I will find

[Ozark Lee]

Removing the panel is easy. I have some tips in this post:

850 sunroof headliner repair

...Lee

[dosbricks]

Nice work, N_D! Besides the number of clamps, as a fellow woodworker, one recognizes the patience required for a repair of that nature.

Years ago I noticed a half inch section of the metal edge around my 850 sunroof glass begin to swell a tiny bit from rust starting underneath. I ran a thin bead of black silicone from a squeeze tube all around the edge prying up the metal a bit with a pocket knife ahead of the silicone to get it under there. About 1/2 hour after applying, I sliced the excess through to the glass with a razor blade. At that stage of curing (give-or-take depending on temperature) the excess will peal up cleanly from the glass. It comes off very stretchy like that goo that holds a new credit card to the mailer. It's way easy to remove--just have to catch it at the right time.

End result has been that it has never leaked since, and it's so narrow as to not even be noticeable.

[rspi]

Man, there is NO WAY I would do all of that work when I can get a replacement glass for about $30 at the junk yard with NO RUST.

[RussB]

Man, there is NO WAY I would do all of that work when I can get a replacement glass for about $30 at the junk yard with NO RUST.

That's because you're in the desert, and rust isn't the enemy it is here in southern New England. The sunroof in both my 850 and S70 are VERY rusted. Maybe I need to contact a junkyard in the southwest?

[JamesUKV70]

This is a common problem here in the UK and I too have done this repair, I just have the rubber gasket to put on then it will be done. I bought a brand new gasket because mine had started to wear very badly, it was a must have item and I could not do without it, over here it costs about £140 inc postage, or $215, a lot of money but well worth the extra expense if you are capable of doing the repair yourself. Your write up is excellent and had I not already done mine, I would have been very happy to follow your instructions.

[RussB]

My best of 2 sunroofs was beyond repair. I bought a used one from Florida that's in excellent shape.

[rspi]

I travel a lot. I'm in Ohio now and will be in NYC and likely Boston within a week. I'd be glad to help you guys with RUST FREE oversized parts. Just let me know, PM or something.