I just had to do this with my 79 chevy pickup. I first tried with the glue that came with the mirror, cant remember the brand but like you I put the activator on and then the glue and held it for a min per the instructions. After that I left it for an hour (instructions said 15 min was good enough). As soon as I attached the mirror it popped right off. I tried some E5000 glue my wife had and that failed instantly. Ordered some of the 3M high bond rear view mirror adhesive from amazon, cleaned everything with acetone and then alcohol. Pressed it on and left it for an hour again just to be sure and for some reason this time it seems to have worked. Its been holding for a couple of weeks now. Everything I have read says that the mount and glass have to be perfectly clean. Only real difference in this last install was I made sure to use plenty of activator and glue.

What I got from amazon -

Amazon.com

 

Work on cool glass. See if there is a grey disc that comes out of the mirror mount, usually secured by a set screw. Clean that and the windshield carefully with a razor blade and some acetone, not laquer thinner, until you are 100% it's all clean and dry. Then an alcohol prep pad, and allow to dry. Get a foot long piece of painter's or masking tape. Use a DROP of actual rearview mirror disc glue on the disc, making sure to glue it in the position that the mirror mount arm will slide down over it when done, beveled edge turned the right way, etc. Apply the small grey disc to the glass and use the piece of tape to hold it. Have a cold beverage and allow to dry overnight. The next day, slide the mirror mount arm over the disc and gently tighten the set screw.

 

I have had good luck with Permatex adhesive. I also put a stick from the transmission hump to the base of the mirror to hold it overnight.

 

Your adhesive should come with a primer and the glue. Both surfaces should be cleaned with soap and water, then both primed and let dry, then apply a dot to the mirror "spot", apply to the glass and hold for 60 seconds then stick with some painters tape overnight.

 

A primer…..
first I’ve heard of it. Poked around the web a little but didn’t see anything that jump right out.
Do you have a favorite?
Thanks

 

If you don't have primer (and use it if ya got it), know that superglue cures with moisture. I had no primer once, and prepped everything as mentioned above on cool glass in the morning. Got the drop on, lined-up and almost touching, then breathed on the glass to fog it and immediately stuck it on. That was about 7 years ago, so far. 🤷‍♂️

 

We have to glue these stupid discs on at work a lot because of having to replace windshields, mirror getting knocked off moving a rifle out of a rack, and the in-car video camera or radar antenna are sometimes mounted the same way. They're a pain but we've gotten pretty good at it!

 

I always use 5 minute clear epoxy , never had one break off .
clean windshield
apply epoxy to base & windshield
hold base in place for 5 minutes
let sit OVERNIGHT before putting mirror on.

 

Thanks all. I now have a new plan of attack.

 

I spent 5 years as a glass installer and can't begin to count how many times I've done this. I scraped the glass and mirror button with a razor blade- 1 pass, squirt primer on the glass and button, 1 drop glue, smash together and held for 30 secs, slipped mirror on and split the scene. Never cleaned the parts with anything, and never had a problem. The trick is to make sure the button is absolutely clean and flat- any residue left on it or knicks from taking it off and it won't work. Best advice- put a mark or a piece of tape on the outside of the glass exactly where you want to glue the mirror, and most importantly- make sure you glue the correct side to the glass!! yup- did that once....

 

I learned years ago that incorrect glue, like superglue, will work. But at some point the mirror will still come off, or be knocked off. And when it does, it will take a chunk of glass out of the windshield with it. I stick with the "correct" stuff and am at peace with that mirrors fall off every couple of years.
Since I have too many vehicles and last time I keep a few glue kits stocked. I used my last one a couple weeks ago and though to pick up a few at the parts store. How about no? When did the price go THAT high. Added four very much cheaper glue kits to a Rock Auto order instead.

 

I stick with the "correct" stuff and am at peace with that mirrors fall off every couple of years.

Yikes! the factory glue lasted 50years. I think I'll still be pissed after just a couple years, At least that's longer than the couple weeks I've getting so far......
I ordered the product Bart recommend

 

"Scuffing it up" may actually be counterproductive to a good bond.

 

I've used the LocTite version with success. Last ones I bought on Rock Auto were the 3M versions at $2.54 each.