H2

How I repaired my delaminating hatch glass

The explanation below is a very loose and disjunctive compilation of several posts I’ve made on this topic. I’m far from being an expert or even a sane wannabee. However, I had to do something since my rear hatch glass was mostly delaminated across the top and I didn’t want to pay the $5K or so I’d heard that a broken rear hatch costs today.

First, I used 3M windo-weld super fast urethane #08609. It’s very black, really nasty stuff. But gives VERY GOOD adhesion. You’ll have to use lots of rags and 3M adhesive remover. I took a chance and scraped off all the paint I could between the glass and the frame (my glass was only delaminated at the top part of the hatch). I then cleaned the area between the hatch and glass very well with acetone and various degreasers...then I did the unthinkable, I flexed the glass away from the metal frame with the wooden part of wooden clothes pins that I'd dismantled and inserted (BTW, I DO NOT RECOMMEND NOR TAKE RESPONSIBILITY IF THIS TRICKY PROCEDURE DOES NOT WORK FOR YOU...I’M JUST TELLING YOU WHAT I DID…AND IT WORKED FOR ME. Your glass could break).

Next I used a caulk gun (very fine bead) to force as much as possible of the urethane adhesive into the crack/opening I’d made with the wooden clothes pins (both sides). I also used a large "doctor's" syringe without a needle in it. Warm black goo works best as it flows into the tight crack better. I also used wax paper to keep the black death goo from sticking between hatch frame and the car frame, resulting in a permantely closed hatch. Then I let the urethane cure.

The repair has worked great for over a year and half now. It was scary but I was willing to take a chance on breaking the rear deck glass. After reading up on this I didn't like the idea of "sawing" the other 3/4 of the panel adhesive loose from the glass with piano wire and regluing the whole window back on. While that may be preferable, I KNOW I'd have broken the glass that way! So, I took my chances and it worked out great for me. I can’t recommend any adhesive other than 3M windo-weld super fast urethane #08609 since it grips like the devil herself on steroids.

Did I say that the 3M glue was nasty stuff to clean off glass or carpet or body parts? Be ready with lots of cleaner and drop cloths. I also sealed the entire perimeter of the glass on the inside and outside with a fine bead that I smoothed out with my finger since the tube of adhesive was large. I don't think I'll ever see a leak at my hatch area. Worked for me and I'd do it again.

While I was at it, I cut a small hole in the hatch weather strip and snaked a small flexible 1/8" hose up it starting from about the middle of each side and up past the hatch hinge. Saved me from buying a new weather strip as it put the shape back in the smooshed down part of the strip. There is now again a tight seal with the original strip. Again, you have to be careful since too stiff a tube might stress things. I like the neoprene sling shot hose when I can find it in small size. It took a while to snake it in there but it works. I've done this on several cars to revive weather seals. I then closed the hole in the weather strip with some silicone and protective wax paper and closed the hatch while the glue cured.

I did not remove the hatch for any of this. Some people do but I think that’s taking some chances. After gluing glass down with the black urethane, I clamped the glass to the frame before the glue cured (wood slats between clamp and car parts), and I put waxed paper around the edges and closed the hatch so it would dry and conform rather than bind. I did a Google search and bought the 3M urethane glue from some place back east. It's not at your local shop unless you live in a large town. Body shops may have it or an equivalent. It comes in a large tube for a caulk gun. I used the whole tube before I was through. Remember, I did not just the delimination but also the inside and outside edges where the glass meets the frame. If you're careful, and use lots of rags and 3M adhesive remover, it looks good.

Also, I used various syringes with long tips...and as wide of holes as I could get to squirt the warmed up glue into the relatively tiny crack I was working the glue into. Too small a syringe hole and the glue won't pump out.

I was fearful of breaking the expensive glass the whole time. The frame is pretty loosey goosey so it flexed enough to allow me to spread the frame from the glass. I dremel-tooled the center out of a flat blade screwdriver to get the specialized molding nuts off. Best to work without the molding where you can. If you drop the molding nuts, they’re hard to see.

Glass shops tend to not want to do this work for fear of breaking the glass. I don’t blame them.

But, I figured, what do I have to lose? I would, however, hate to try and buy another rear glass. Finding one is one thing and shipping it safely is another. And the work looks good.

I think I said it a dozen times already...but this 3M black urethane glue is REALLY messy stuff so use drop cloths and lots of rags with 3M adhesive cleaner before it dries. It's hard to get off and seems to get on everything. Also, I can't emphasize cleaning the glass well beforehand so it will adhere. Have 4 times as many rags for cleaning on hand than you think you’ll need.

I was VERY careful (and scared the whole time that I was going to crack the glass). I keep saying it, no guarantees for you...but it worked for me. My delamination was slightly more than half of the top frame so it was harder to flex the thin frame to get sealant in. I used a very thin razor blade to scrape as much of the old stuff off as I could. If the paint's not sticking well, it'll come loose soon. And if it doesn’t come off with a razor I figured it still had some life left in the adhesion. Use Made in USA single edge razor blades. They’ll outlast the Made in China blades 12 to one and may save you a cut finger.

The nasty black glue gets on everything easily so I spread out a big disposable drop cloth (not plastic) in the trunk, removed all removable pieces of trim (lost a few slotted screws), sat the sealant near the furnace in the house for the night to warm it and improve flow viscosity. Using various small syringes that I filled with the sealant...syringes w/long thin tips that I had to clip off to get an acceptable flow and still be able to work the tip into and between the center of the glass/frame area...I squirted like heck..and it is hard pushing the glue out of the syringe tip. (Remember I separated CAREFULLY the frame from the glass just enough that I didn't want to break the glass but enough to get the glue in. When I removed the wooden clothes pins that were holding the glass and frame apart, it would squish the sealant over the inside. Then I removed the extra goo that squished out of the crack with the 3M cleaner and rags. Just barely spread the trim pieces...don't bend the trim or it will not be easy to get it back into their original place, if ever. A new deck is hard to find and expensive.

As mentioned, before I did all the above, I razor bladed off all the paint I could, then used acetone and alcohol to clean the rest to get a good adhesion surface. I thought of using some 600 grit sandpaper on the glue surface to get more grip for the adhesive to cling to but there wasn't room for the sandpaper. A larger delimination might allow this and, actually, be easier than the repair I made.

Once the clothes pins are removed, I used screw clamps to hold everything in place while the glue cured. Another balancing act. I didn't clamp tight..but just enough to be have a firm connection without risk of stressing and breaking the glass. I think I used 4 small clamps with wood protection. Oh yeah...then I let it sit for a FULL WEEK to cure before driving the car. I wanted a complete cure before moving anything. Think about it, air cures the urethane and if it's relatively tight like it's supposed to be, air won't be getting to it for a while.

I don’t think the repair will ever come loose because the urethane glue sticks like the Devil's army. If you try this, good luck! I'm sure that this was easier than pulling the whole window off.

Actually, the fix really looks good. Not totally professional but only a glass guy would probably notice. I do, however, need to obtain some of the UV resistant flat black paint and prep the outside of the glass, mask it, and paint it to keep UV rays away from the urethane glue and the rest of the glued glass. It's the sun and UV rays that helps deterioate the original glue causing the delimination.

Actually, it’s a relatively simple job but fear of cracking the glass makes your adrenaline flow a bit.

Harvey

User 41221

I've personally repaired about 12 hatches at this point, and am convinced that the only way to do it properly is to remove the glass in its entirety, clean it everything, and then use 3-M Window Weld (or equivalent product, they are out there and are cheaper, ask for it at your local Automotive Paint shop) and the corresponding primers for the metal frame AND the glass. Its a pain, but if you work slowly, it's doable, and should last for the remainder of th elife of th ecar, provided you do two things:

1) Use WAY more adhesive at the top of the frame than the factory did, so that it seals all teh way to the edge of the inside of the frame. It will give you roughly twice the sealing area than the factory job did.

2) Paint a black strip (flat black spray paint works fine) over the outside of the glass along the top edge, so that UV rays can't deteriorate the primer seal between the glass and the adhesive (as noted by Harvey). I would suggest you do this on ANY hatch that has a good seal.

I've seen any number of temp fixes done at just the top of the hatch, but have my doubts that it can last, since you can't reprime it properly before applying the adhesive.

Harvey, you are right about Window Weld being nasty stuff! lol I usually pick my worst clothes and just throw them away each time I do a hatch.

Regards,

RajDatta

Owning a coupe, we all have to look into this at some point. I don't need to do anything yet but its good to know we have expert DIYers with hands on when its time.
Thanks guys.
Raj

potent951turbo

I didn't read your whole method but it sounds very similar to the one I used on my 951 hatch. My hatch was also seperated at the top edge only. I removed the spoiler and upper metal trim piece that just pops on the top edge. Then I got a bunch of wooden coffee stir sticks and slowly pushed them in between the glass and frame so I would have enough room to put the window adhesive in. The I went to a well known glass shop and bought the 3M brand they use that doesn't require a primer and went to work on getting as much as I could in the edge. Afterwards I removed the wooden stir sticks and put spring loaded clamps along the edge. So far its held for well over a year and I haven't had any problems.

H2

SH944...you did it the RIGHT way and it really should last the life of the car if you had a clean surface and good adhesion. I'd be surprised if I experienced delimination in 10-15 years...but if that were ever to happen, I'd go through the process you did. Very tedious work sawing the glass off with a piano wire when the glue that is stil there is adhered well! Also, two people are required to handle the hatch so you don't break it.

Potent, you and I essentially did it the same way.

When a glass shop is afraid to touch a job, sometimes you're forced to do it yourself.

Harvey

PorscheFanatic202

Can we get some long term updates on this? It would be a great data point