The first sign of this problem is when the lift struts for the rear window of my hard top could no longer lift the window all the way up. That's a sure sign that one of the struts has died, and the remaining one is supporting all the weight of the window glass. That means that twice as much weight is now being supported at the mounting point of the remaining good strut.
The problem here is that the factory fiberglass hard top is actually a two piece design, and the window struts are attached to only the inner shell. Over time, placing too much weight on the window struts will cause the two fiberglass shells to separate along the window frame where the struts mount. When this happens, you then have twice the intended weight being supported by a shell only half as thick as intended. That's bad.
Once you've got the weight shared by two struts again, you can glue the fiberglass shells back together. I used a 2-part epoxy made for patching fiberglass, but there are probably other epoxies that will work, too. Here's the basic steps:
- With the rear window open & supported, unbolt the strut support from the hard top and get it out of the way.
- Pull the weather-stripping back out of the way.
- Mix up your epoxy per the instructions on the package using a disposable stick. The thinner & flatter the stick, the better. I used a toothpick. You don't want to get this on your skin, so wear gloves if possible. You probably don't want to get it on your tools, either.
- Using a wide screwdriver or similar object, pry apart the two halves of the hard top where they've already become separated.
- Using the stick, shovel as much epoxy as you can into the gap between the two halves of the shell. Part way through the process, let the two halves come together to smush around the epoxy, then quickly separate them again and continue shovelling. The hard part here is that the gap runs vertically, and the epoxy wants to run along the crack rather than deeper into the crack. This process would work much better if you could lay your top down on its side in the lawn so that gravity would pull the epoxy deeper into the gap.
- Once you've applied as much epoxy as possible, clamp the two shells together with several sturdy clamps, then wipe away the excess epoxy that oozed out of the gap.
- Let it sit as long as necessary to completely cure. Don't rush this part. When done, reassemble the strut.
The first time I performed this repair, it held up great until the opposing strut died again. When it failed again about ten years later, I did it the same way. If I have to do this a third time, I'll definitely lay the top on its side for more thorough application of the epoxy.
Update: This second patch snapped open again one cold, winter day just a few months later. Laying the top on its side will have to wait until summer.