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Reattaching a rearview mirror

Posted by kudzu9 (My Page) on
Fri, Mar 9, 12 at 0:31

I just slammed the door on my 20-year-old van and the mirror fell off the windshield. I know you can buy a kit for $6-7 at the auto parts store to re-glue it, but is this really necessary? Can I use either super glue or a two part epoxy to reattach it instead?


Follow-Up Postings:

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RE: Reattaching a rearview mirror

No you can't


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RE: Reattaching a rearview mirror

The mirror re-gluing kits use cyanoacrolate type adhesive (same as crazy glue but may have a different formulation).

The secret to a sucessful repair using this type of adhesive is that it will not stick to itself! That is, it will not adhere well to a surface of the same type of adhesive that has already set and is solid. Both surfaces must be free of old adhesive. Therefore, if you have a failure, you can not re-do by trying again over the prior adhesive. All of the prior adhesive must be removed before trying again.

TIP: Look closely at the mirror mount. Most have a small block that can be removed from the mirror proper. If a set screw is pesent, loosen it and slide the block off. Some are friction fit and will loosen by a light tap. before you begin the glue job, take the small mounting block off. Its much easier to handle the small block when gluing on than the entire mirror. Also, after the initial setting of the adhesive, the small block presents low force to the bond while the bond strengthens.

Clean both surfaces. You may have to resort to a razor blade. remove all races of the old adhesive. If the kit contains an accelerant, apply to only one surface. Let the solvent evaporate. Apply a few drops of adhesive to the other surface, position the part (without touching) and when eady, push the two surfaces together. It is critical during the first few seconds that the parts do not move. During this time, the liquid adhesive is flipping to crystaline form and will be damaged if shifted. The 'grab' is amazingly fast. Continue to apply pressure for one minute. The bond will arrive at 50% strength in one minute at 70 F; longer time is required for colder temperature. The bond will continue to gain strength over the next 24 hours at 70 F; it will take longer at lower temperture.

After the initial set, wipe away excess adhesive outside the bond line.

This type of adhesive is slowly attacked by moisture over time. For long term installation, seal the bond. There should not be any glue sticking out from under the sealant. The sealant should cover the bond edge/line and seal to both top and bottom pieces thus sealing the adhesive from moisture. Sealants having acetone solvent are not recommended since acetone may attack the adhesive. Only a small amount of sealant is needed, just enough to form a fillet between the mirror mount and the glass.

The sealant is optional. I've made repairs without it that have lasted more than 5 years and was still there when the vehicle was either junked or sold. (I use cyanoacrolate adhesives to apply strain gages and the use of a sealant is standard procedure for long term installations.)

The adhesive will support the weight of the mirrow at 50% strength (at 70 F). However, at this time of year, it is very likely you have colder surfaces to work with, therefore it recommended to wait for an hour or two before re-attaching the mirror. If you can wait a day, do that.

Attempting to attach the mirror mount at temperature of 32 F and lower may fail. Look for recommendations on the adhesive kit.


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