Originally Posted by mach2plus

Well, I reattached my rear window to my convertible top and now only time will tell how long my repair will last... But hey, the ragtop was in like new condition, so it was worth a try, given that a new top will set you back $2 grand or so. And besides, only we motor heads know the sort of sick satisfaction one feels in being covered in sticky black adhesive and smelling like gas, right?
Total Cost: $50
Total Time: About 2 Hours
Parts and equipment required
Caulking Gun
Several Single Edge Razor Blades
Window Cleaner
Several clean rags
Several towels
Dabber (I used an acetone cleaned PVC cement can dabber)
one tube 3M brand # 08609 Windo-Weld Super Fast Urethane Adhesive (Autozone $19)
one bottle 3M brand #08681 Single Step Primer (via internet, Fox Run Tools $29 delivered)
one roll masking tape, 3/4 wide or so
regular screw driver, about 3/8 inch wide tip
stop watch or timer
some gasoline for cleaning up mistakes and hands
Step-by-step Repair
Note: I would recommend that you read these instructions thoroughly before proceeding, and that you do a dry run beforehand, so you know the procedure and are assured that this technique is applicable to your situation.
1. Leave the top in the fully closed and locked position, and place both of your car seats as far forward as possible.
2. You will note in my pictures that I used both cork liner material and towels inside the rear window area. I used the cork liner so that: (a) the window could drop down and I could have room to apply the primer to both the glass and canvas, and (b) to protect my car finish from the window edge and any possible primer drips (which didn't happen). I removed the cork after applying both the primer and adhesive, and then placed the towels against the window to support it while I squeezed the adhesive out and while it cured overnight. I also used the towels for window support while I scrapped the old primer and adhesive out. note: my window was still securely attached for about 2 feet along the top, so I just popped the unattached portion of the glass outside of the canvas for better access while scrapping. Your situation may be different, but remember that there are 2 defroster wires located on each side of the window, so be careful! Thankfully, the factory left some slack in my cables, but the connections are fragile. BTW, I couldn't detach my connectors.
4. Using masking tape, place tape all along the edge of the window, about 3/8 inch from the edge of the old primer line (see picture), which should be visible on the outside edge of your window. Use a single edge razor to trim the tape as necessary. This tape will give the new primer a sharp clean edge, and later serve as a real good way of orienting the window in the canvas opening.
5. Now, using single edge razors, remove all of the old adhesive and the primer from the window edge. At first thought this may appear to be an easy task, but it's not, as the old primer is a freaking PITA to remove! Once it is all removed from the glass, use a razor to scrap the canvas where the original window adhesive used to be attached. Go back and forth, keeping the razor edge 90 degrees to the canvas, and scrap as much of the old, loose adhesive off as possible.
5. Clean the glass until it is spotless, and the canvas as best you can, removing any loose debris, etc. I used an ammonia based glass cleaner, acetone, and some clean lint free rags on the glass, and some lint free rags and some sticky masking tape (as tack) to clean the canvas.
7. Protect the interior of your car surface somehow (see 2, above). Shake the 3M Single Step Primer until you can hear the ball rattle freely, and then continue shaking for 60 seconds. Using a dabber (this is the key to a perfect primer application), apply the primer from the window edge right up to the masking tape. It goes on very smoothly and evenly, and this step couldn't be easier. The 3M Primer instructions, found on the internet, also said that the primer could be used on metals, plastics, and PVC, so I also applied the primer to my canvas where the adhesive would eventually be. Now, hack your watch and let it all dry for a minimum of 10 minutes (see primer instructions!). After the primer has dried, simply pull the masking tape off and marvel at the nice clean primer straight edge you created!
8. This step is the hardest part, so prepare for it. Using the caulking gun, apply the 3M Windo-Weld Urethane close (but not on the window edge. Remember, you will be squeezing most of it out) to the edge of the glass, directly on the primer. I applied a thick 1/4 to 3/8 inch bead. Once completely applied along your window edge, used a single edge razor to flatten the adhesive out slightly, and then, using your towels inside your car, place them against the glass so that the window is now flush up against the canvas opening, and offering firm support. Now, using your fingers and working quickly while the adhesive is still workable (see instructions), press the canvas against the adhesive along the entire window edge, using your new primer edge, as necessary, for orientation within the opening. I did this 3 times with my fingers around the canvas edge, and by feeling the edge of the glass through the canvas, you will definitely be able to tell how much glass/canvas adhesive contact area you have established. Once satisfied with my window orientation, I then used a flat (straight) screwdriver edge to further press the adhesive onto the canvas all along the glass/canvas contact area, and as you can see in the pictures, all the excess adhesive comes out from under the canvas edge onto the glass, where you can later remove it perfectly, once it is cured (step 9).
Note: I originally thought that this step was going to be way more complicated, and that I was going to have to devise some sort of clamping system to hold the glass (which is curved) and adhesive together until it was cured. But having experimented with the primer and adhesive the previous day, I learned that the adhesive (a fast curing urethane) was thick and extremely tacky, and that it wouldn't be necessary to use any clamping system at all (fortunately, this all proved to be true) The towels behind the glass proved more than adequate in holding the glass in place, and I didn't need to use any suction cups to hold the glass taut. BUT, you need to work quickly here, as the urethane sets up quickly, so keep pressing the canvas down in a manner that squeezes the excess urethane out from under the canvas and on to the glass, where you can later remove it after it dries. You can now see the importance of using the masking tape too, as it allows you to make a perfectly clean primer line, which allows you to orient the window perfectly in the canvas opening.
9. I waited 24+ hours for the Windo-Weld Adhesive to cure before attempting to remove the excess. Using a single edge razor, CAREFULLY cut (trim) the excess adhesive where it meets the canvas. Your first series of cuts will be straight down and into the adhesive directly along the canvas edge where the excess adhesive meets the canvas. This adhesive is some freaking tough stuff, so it may take you several cuts into the excess adhesive until you get through it and contact the glass. Now, CAREFULLY trim under the excess adhesive, cutting it (and the primer) just up to the point where you made your first downward cut. This is critical, as you don't want to cut out any of the adhesive which is under the canvas, which is obviously securing the window to the canvas. You'll get the knack. Now, refer to the picture, and holding your single edge as shown, remove the excess adhesive that you've now prepped for removal. By holding the razor as shown, you will not cut the canvas, and will cleanly remove the excess adhesive. Once the majority of the adhesive is removed, you can then spot trim and clean as necessary.
As can be seen from my final picture, I removed all of the primer and adhesive right up to the canvas edge, and I can't tell my window reinstallation from factory new. Now, we'll see how long it lasts...
Best regards -- Bob