Hatch glass hinge separation

Discussion in 'Exterior' started by Larryjb, Oct 12, 2019 at 7:46 PM.

  1. Larryjb

    Larryjb Full Access Member

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    After an extensive google search, I settled on 3M Windo-Weld (08690).

    As I removed the old hinge, I noticed that the original adhesive did not actually adhere the metal hinge itself to the glass, even though there was adhesive between the hinge and glass. Yet, this hinge has lasted 17 years. I also noticed that the adhesive completely covered the hinge and was spread out over 12" (a good 6" both sides of the hinge), and was built up at least 1/8" over the hinge. This had lead me to surmise that the adhesive is not relying on adhering the hinge to the glass, but rather, using the adhesive to keep the hinge clamped to the glass. With this in mind, this is what I did:

    1) Cleaned off all surfaces as much as I could, reasonably. I used a drum sander on my dremel which made quick work of removing old adhesive, even down to the glass. I did use a rotary brush on the hinge to remove as much old adhesive as I could. I removed enough old adhesive on the glass so that I could build it up again over the hinge, but left enough so that I could easily locate the hinge in its original position.

    2) Washed the entire area with water. Because the area being repaired was well sanded, I felt it wasn't necessary to use any detergent or other solvent. In fact, the urethane sealant cures better with a little moisture.

    3) Warmed up the tube of 3M 08690 inside a ziplock bag, in a sink of hot water.

    4) Applied some painters tape to prevent over covering the area with adhesive.

    5) Applied adhesive generously to the glass where the base would be located.

    6) Pressed, by hand, the hinge to the glass, and wriggled it into position until I could feel it "lock" into the original position.

    7) Applied more adhesive so that I would have a good 1/8" on top of the hinge, and spread it out about 3" past the sides of the hinge. I also smoothed it over as best I could with my gloved hand. The repair doesn't look pretty, but no one will be looking at it.

    8) Set up a heater to increase the curing temperature to 90°F. A cure to 150 psi will be achieved between two to four hours, depending on relative humidity.

    It is sitting curing right now, so I don't actually know if this is going to work or not. But, judging from what others have done, this repair with this adhesive has lasted several years.

    It's my understanding that JBweld will crack out as soon as the heat expands the metal hinge. The only reasonable adhesive to use is this stuff from 3M, as far as I know.
     
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  2. Larryjb

    Larryjb Full Access Member

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    There is something else I noticed about the old hinge mounting. The adhesive from the factory did NOT cover the hinge very well. The hinge has several holes that get filled with the urethane adhesive, and covered over the a good 1/8" of adhesive. The holes of the hinge were visible on this hinge. The holes on the other hinge, which is still holding, are not visible, and still well covered.

    What could this mean? If your hinge has not yet separated, you might be able to prevent a hinge failure by examining the hinge. If the adhesive does not adequately cover the hinge base, you could try lightly sanding the adhesive, and applying more on top of the original adhesive. If the original adhesive is urethane, and you use the 3M 08690, it might bond well enough to prevent the hinge from separating.

    Just a thought, and could be worth trying.
     
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  3. Larryjb

    Larryjb Full Access Member

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    I just finished installing the glass into the truck. The urethane is still very squishy, but not tacky. The hinge does not move. I'll leave the glass lift struts off for awhile until the urethane has set up completely.

    I had a heck of a time lining up the holes to insert the hatch, but I got it in finally.
     
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  4. ScottyBoy

    ScottyBoy Full Access Member

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    I've heard of this happening to a LOT of Tahoe, Yukon, Suburban owners. Thankfully, I have not had any issues with mine. But then again, I have probably only actually opened my rear glass about a dozen times at most during the entire time owning my truck, and I've had it since 2006. I usually just open the entire rear hatch, not just the glass.
     
  5. Larryjb

    Larryjb Full Access Member

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    We use the hatch a lot, so maybe that's why it failed. There's nothing like having the entire contents of the cargo area fall out the back when you're parked on an upwards slope. Cargo nets help, but aren't perfect.
     

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