First hot day, mirror falls off

Last year I bought a couple of used cars, and when it got hot the rear view mirrors fell off both of 'em. So I glued them back on with the
glue kits they sell for that purpose. I followed the directions, cleaned carefully and let the glue harden over night.
It got pretty hot this week, and they both fell off again a few days apart.
So I'm wondering if the windshield shades I use in both cars are the problem. I use the kind with fabric and wire frames that twist and fold up into a very small space. They push a little against the mirror, and while they keep the interior of the car cool, I think the windshield gets pretty hot, maybe hotter than without them.
Any suggestions on this? I'm particularly interested if you live somewhere hot like Arizona. What's your experience? -Paul
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I'd trim away the windshield shades around the mirror-mount to reduce pressure against the mirror. I also have had better success with a good superglue or 2-part epoxy than the glue kits sold to re-attach mirrors.
Suggest you also tape the mirror mount on after glueing, to put put pressure on it against the glass while the adhesive cures.
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The kits I tried used superglue (at least, it looked the same and smelled the same). I was re-installing the mirror annually for a while; JB-Weld (a two-part epoxy sold at auto parts stores) fixed it permanently (so far; it's been over a decade).

Definitely.
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Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
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Joe Pfeiffer wrote:

Thanks for the tips. The "official" rear view mirror adhesive seems to be flexible. My kit came with a razorblade to remove the old stuff, and it's like a patch of clear plastic- bends, stretches, comes off in one piece. Maybe they figure it's better to have it come off once a year rather than risk damaging the windshield. Flexibility probably helps with the differential thermal expansion between the glass and the metal piece too.
I bought a kit to replace the first mirror when it fell off, and so I used that to glue both of 'em on this time. If they come off again, I'll try the 2 part epoxy. I use that all the time to repair other things. -Paul
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snipped-for-privacy@egine.com writes:

Your kit is substantially different from the kits I got (at least one from Mopar, at least one from NAPA, don't really remember how many from each source) -- mine had an ampule of what I took to bes uperglue and other accessories. So your mileage will most assuredly vary on how well the kit works.
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Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
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Joe Pfeiffer wrote:

I don't remember what brand the other kits I used were, but this one was a Permatex kit. It came with a razor blade for removing the old glue, a strip of sandpaper for polishing the metal mirror mount, a wipe with sealer/accellerant, an ampule with the adhesive, and an alcohol wipe for cleaning the felt tip marker ink off the windshield.
I only remember the accellerant and adhesive being in the other kits.
One other thing- seems like it always leaves the adhesive on the windshield, so it doesn't stick as well to the metal... -Paul
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The secret with these kits to make a good bond is to use an extremely SMALL amount of the glue, and the second you put the half-drop on that is required you immediately smack it squarely against the winshield, hold it against the winshield with as much pressure as you dare, and DO NOT MOVE IT until the glue hardens in a couple minutes. Most people that don't do these regularly use way too much glue, not enough pressure, and move the damn thing around getting it positioned after putting it against the window. And you also have to have a perfectly clean surface on each side, and the kit needs to be pretty new.
Superglue is one of my least favorite adhesives. It has practically zero shelf life after manufacture, no shelf life whatsoever after opening, won't glue most plastics worth a damn, won't glue anything porus worth a damn, sets up almost immediately, and can't stand shear shocks. About the only things it's good for are gluing skin together.
The two part, long setup epoxies are the best. JB Weld is the most well known, but any industrial supply house sells long-setting epoxy that has the same 24 hour setup time that JB Weld has, and holds with the same ability. They also have a huge shelf life. I remember getting a baby jar full of epoxy and a baby jar full of hardener from by Dad's workplace from the taps on the 55 gallon barrels of industrial epoxy, and I used those for at least 10 years before the hardener finally ended up solidifying.
Ted
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