Rear Window - Gasket or Sealant?

8thTon · Feb 11, 2019

I’ve been battling a roof leak which I initially thought was the brake light - it may have been leaking there too but clearly the window was a problem. I bought new barbed plastic clips and got a couple of the nylon sockets at the junkyard, and on Sunday I had just enough time to do the job. I wish I had taken pictures but I was pressed for time.

Once I got the window out I saw the problem was the good work of the folks at the NJ assembly facility. There was either a gasket or a 1/4” wide bead of sealant that went over the three studs at the top. However between the studs it dooped down as far as possible on the flange, leaving a low spot. The sealant appeared to have no contact on the side that was leaking.

I coated that gasket/bead liberally with 3M weatherstripping adhesive, both on the truck and the window, and put it back together. I hope it seals but have not tested it yet. Still, that low spot will trap water and any little hole will let it in.

If I have to do it again I want to scrape that poorly installed stuff off, but what do I replace it with?

Shran · Feb 12, 2019

I would try this stuff:

adsm08 · Feb 12, 2019

I used Permatex "The Right Stuff". It's basically black caulk in a tube.

But my rear window doesn't leak.

8thTon · Feb 12, 2019

Hmm, had I seen those at AZ I would have probably gone for either, but if I do it again I want to replace what was there from the factory. That fills a fairly thick gap between the body and window (I did not measure it but somewhere around 0.100"). This is why I could not tell if it was some formed gasket material or just a bead of thick sealant - I'm leaning toward the latter.

I'm starting to suspect that someone had something heavy but soft leaning against the back of the cab & light. There are no marks but I reshaped the edge of the roof metal when I put the light back in last (so it met the gasket in the middle properly), and there is the smallest of gaps at the very top edge of the rubber window gasket right where it leaks (maybe 0.010" or so) - this is not the real seal inside, it is more decorative. Maybe someone was standing in the bed and had their knee against it or something. This may have separated the old seal from the window inside.

So anyway if I have to redo it I'm going to find some thick but pliable and non-hardening sealant to use that can bridge that gap, and apply it so there is no dip down between the studs that can hold water.

Shran · Feb 12, 2019

You want windshield urethane if you want a permanent seal. I like the flowable stuff for repairs because it literally flows in - it's very thin. But not so good for filling big gaps.

You could also use RV/mobile home window putty. Comes in a roll, can get it at walmart, never hardens and works really well for windows that are bolted on and squeezed up against another surface.

8thTon · Feb 12, 2019

Shran said:
You could also use RV/mobile home window putty. Comes in a roll, can get it at walmart, never hardens and works really well for windows that are bolted on and squeezed up against another surface.

Thanks! This sounds exactly like what I will want if I have to go back in.

91stranger · Feb 18, 2019

8thTon said:
Thanks! This sounds exactly like what I will want if I have to go back in.

Its also called butyl tape or putty tape. We sell for less than $10 a roll and a roll is 1/8" x 3/4" x 40'. So you get quite a bit. We use it as a basic water barrier for windows and doors and some fixtures and then seal around them using dega seal. This is like silicone on steroids lol. silicone will peel off really easy where as dega seal does not lol. Combination of these two things will guarantee no more leaks if done right.

Rear Window - Gasket or Sealant?

8thTon

Well-Known Member

Shran

Junk Collector

adsm08

Senior Master Grease Monkey

8thTon

Well-Known Member

Shran

Junk Collector

8thTon

Well-Known Member

91stranger

Well-Known Member

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