Sunroof rust repair: Madness may ensue, as usual.

Post by **Growlerbearnz** » Wed Jun 21, 2017 3:57 am

sinjin wrote:So...I have a 96 L400 LWB with some rust on the middle of the roof between the windshield and the front sunroof. What should be done about it?

Right now, as I bleed from various cuts and smart from weld burns, my inclination is to say "burn it to the ground and claim the insurance"

Is the rust bubbling through from the inside, or has it started from paint damage on the outside?

From inside- don't ignore it (like I did), remove the roof lining and figure out what you're dealing with. If you catch it in time you might be able to clean it up, paint it with a rust-converting epoxy, and then hose it down with rust preventative wax spray.

From outside- clean, remove all rust, prime with rust killing primer, and spray with a colour matching top coat.

NewDelica91 · Post by **NewDelica91** » Wed Jun 21, 2017 6:13 pm

Growlerbearnz wrote:Leaks are usually just clogged drains, the two in the front are easy to get to, but the ones in the back are hidden behind the roof lining. The ones in the back are also the ones that rust out.

I'm circumventing the leaks by gluing the glass directly into the body, like a bonded on windscreen. It won't open, but I'll keep the sunshade so it won't be too hot. As well as reducing the risk of leaks, I'm also gaining an extra 30mm of headroom by deleting the opening mechanism. I might even redirect the rear aircon forwards and over the glass to help cool it down on hot days.

Hey is there anything in the manuals for locations of the drain lines for the sunroof?

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Post by **Growlerbearnz** » Thu Jun 22, 2017 3:02 pm

I don't think so. The rubber hoses run above the roof lining and down the rear pillars, and down the B-pillars. You can see them sticking out just behind the wheels (both front and rear). The front lines can be cleared out without removing anything (open sunroof, point compressed air at visible drain hole), but the rear lines require removal of the rear headlining.

I'd take a picture for you, but mine have been removed and satisfyingly flung in a corner.

NewDelica91 · Post by **NewDelica91** » Thu Jun 22, 2017 8:56 pm

Growlerbearnz wrote:I don't think so. The rubber hoses run above the roof lining and down the rear pillars, and down the B-pillars. You can see them sticking out just behind the wheels (both front and rear). The front lines can be cleared out without removing anything (open sunroof, point compressed air at visible drain hole), but the rear lines require removal of the rear headlining.

I'd take a picture for you, but mine have been removed and satisfyingly flung in a corner.

No worries buddy! I bet you were happy to toss them to the corner?

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Post by **Growlerbearnz** » Fri Jun 23, 2017 12:02 am

And we're making progress: the new roof panel is fitted and welded in place. It doesn't look like much work, but it's taken 3 days and the workshop is a mess.

Everything aligned and held in place with Cleco temporary fasteners:

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Rather than a proper butt joint, I'm making a joggled lap joint. It's a bit amateur and can create a rust trap if not sealed properly, but the roof panel is incredibly flimsy and a butt joint would create more distortion than I'm willing to deal with.
Plug welds along the seam:

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Grind the welds back until everything is smooth again:

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Now I just (just!) have to prime everything, reassemble with panel adhesive, and then I might be able to install the glass and then paint it.

NewDelica91 · Post by **NewDelica91** » Fri Jun 23, 2017 10:45 am

Looks awesome!

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Post by **Growlerbearnz** » Sat Jun 24, 2017 12:02 am

All scrubbed, masked (with newspaper because of course I ran out of masking film), and primed with epoxy.

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Now we let it cure for a day or two, and then glue in the roof bows and other structural bits (which are also primed and ready to go)

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NewDelica91 · Post by **NewDelica91** » Sat Jun 24, 2017 9:35 pm

Whatever works buddy!

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javabob · Post by **javabob** » Tue Jun 27, 2017 8:18 am

That is looking fantastic Growler!
What panel adhesive are you going to use?

Post by **Growlerbearnz** » Tue Jun 27, 2017 3:24 pm

javabob wrote:What panel adhesive are you going to use?

I've used Sikaflex 221 (moisture-curing polyurethane adhesive sealant) for adhering the roof bows to the roof skin, and for seam sealing the lap joints on the inside. Like all urethane adhesive/sealants it's flexible, has great bonding, and is paintable with any paint system.

The glass is installed with Sika Tack-Drive windscreen adhesive. Being an OEM product and airbag rated it's probably overkill for a sunroof, but I really don't want it to leak. The downside is it requires use of Sika's special surface prep/cleaner, and special primer- so your reasonably-priced $20 tube of windscreen goo turns into $100 of single-use products. Ugh.

EDIT FROM 2 YEARS IN THE FUTURE: Don't use Sikaflex 295UV. It's not designed to adhere to glass. Ask me how I know. Ugh.

Once the roof is painted I'll fill the gap between glass and panel with Sikaflex 295UV, a marine-rated UV resistant sealant. It should make a pretty looking filler strip, and not break down in the sun.

Post by **Growlerbearnz** » Wed Jun 28, 2017 12:00 am

Roof bows and glass support frame are all in place, and the glass is finally installed. In theory it's watertight and driveable now, though it's still not pretty.

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Matte black primer hides all sorts of nastiness, but a light application of the longboard sander shows up just how much work I have ahead of me before I'm able to paint it:

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The new piece of roof is nice and flat, but the old roof has lived a tough life.

NewDelica91 · Post by **NewDelica91** » Mon Jul 03, 2017 8:42 am

That is some awesome work!

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Post by **Growlerbearnz** » Mon Jul 03, 2017 3:54 pm

The work is not feeling particularly awesome right now. This has been my life for the last 5 days:

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Ugh. Using filler feels like defeat, but this roof panel is just ridiculously flimsy. You can dent it with your thumb. Shrink out one dent just a fraction too far and another pops in a foot away. Shrink out a large dent and you change the curvature across the whole roof, which makes the ridges look like buckled train tracks.

I'm nearly at the point where my irritation exceeds my standards, which means it's almost time for paint!

NewDelica91 · Post by **NewDelica91** » Mon Jul 03, 2017 4:40 pm

It's looking awesome! Great things take time.

Post by **Growlerbearnz** » Fri Jul 07, 2017 1:29 am

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The roof is finally in (gorgeous mint green) primer, ready for paint. And of course the painter is away on holiday until next week.

Time to work on the interior then.

Not pictured: fitting the sun shade. Basically, I took the old sunroof mechanism, removed anything that wasn't needed any more (motor, sliders, massive steel brackets) leaving just the sunshade, and screwed that to the inside of the roof. More pictures later.

I'd previously measured the roof lining, and it looked like I could reconfigure it to make it work, rather than having to make a whole new liner from scratch. Time to find out if my measurements were correct...

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Hey! Not bad! Right. Duct tape first, to hold the fibreglass in:

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Steel plates to hold the edges in alignment

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Fill the gaps from behind with chocolate frosting... errr, epoxy with fairing filler

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And fibreglass.

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Neat! We'll find out tomorrow if it worked.