Windshield seal question

In removing the windshield and seal, i found black rtv all around the pinchweld. Is this factory rtv? In watching windshield install videos- I havent seen anyone use rtv. Any thoughts anyone?

Warren Lovell said:

In removing the windshield and seal, i found black rtv all around the pinchweld. Is this factory rtv? In watching windshield install videos- I havent seen anyone use rtv. Any thoughts anyone?

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Starting in 1983(I think) it was required for all glass installers to start using urethane to retain the seal and help prevent glass ejection in case of a crash. Any car taken to a glass installer will have urethane used to retain the seal. An at home install isn't required to use urethane, but it is a highly recommended practice.

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If'n I'm not mistaken, the urethane that is used is much stronger stuff than black RTV.

Most definitely. We done a test on a demo derby car one year. I had a door that the latch would not latch on the right rear door. We put a few tubes of urethane caulking in the door jam and some Lords 2 part adhesive. Put the safety chains on the doors. After the derby we tried opening the door and as a back up hooked the strap to the door and ripped the outer skin from the door shell. Where the adhesive was the door would not reopen even with the hinges unbolted. Amazing. We glue panels on vehicles everyday and that is how a lot of he new trucks are built. Makes for a stronger structural strength then bolts alone. Good idea to pull the windshield out of any older vehicle when you are painting it. That pinch weld hides a lot of puss and rust. You are just wasting a lot of time not to remove all the glass on a steel cab.

MarcusOReallyus said:

If'n I'm not mistaken, the urethane that is used is much stronger stuff than black RTV.

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I was assuming he thought it was just black rtv, urethane doesn't dry hard, and remains slightly pliable.

It's also a bear to remove, best success I've had was those strip discs you can put in a drill. But even then they clog up fast.

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The windshield is a structural part of any automobile/light truck.
By adding adhesive, it bonds the glass to the steel and creates a much stronger driver/passenger compartment.
This was one of the many items mandated by the NTSB for safety years ago.

It might not seem like it would work since glass breaks, but it does indeed work very well with the strong adhesive that’s used.
Combinded with the lament that is layered inside the glass to prevent large pieces of glass from flying inside.

The majority of the time it takes to replace a windshield is removing that adhesive.
Very strong and difficult to remove.

RTV is a completely different animal.
The glass would pop out with ease if it were used instead of the windshield adhesive.

Most parts stores stock it.
A standard caulk tube is about $35-40.
Brand was 3M

cucvrus said:

Most definitely. We done a test on a demo derby car one year. I had a door that the latch would not latch on the right rear door. We put a few tubes of urethane caulking in the door jam and some Lords 2 part adhesive. Put the safety chains on the doors. After the derby we tried opening the door and as a back up hooked the strap to the door and ripped the outer skin from the door shell. Where the adhesive was the door would not reopen even with the hinges unbolted. Amazing. We glue panels on vehicles everyday and that is how a lot of he new trucks are built. Makes for a stronger structural strength then bolts alone. Good idea to pull the windshield out of any older vehicle when you are painting it. That pinch weld hides a lot of puss and rust. You are just wasting a lot of time not to remove all the glass on a steel cab.

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I bet the door failed before it opened.
I’ve seen demonstrations of metal tearing away and the structural adhesive holding as designed.



This is structural 2-part adhesive for aluminum.
Incredibly strong and is used in New helicopter assembly and is also used for repairs.
Different part numbers of adhesive used depending on location.
Sets up like steel and is stronger that the aluminum itself.
Bonds much stronger than bolt/rivets ever could.
Used this on my S-280 shelter.

Windshield adhesive isn’t this strong but definitely does the job.

If anyone substitutes RTV in place of the required adhesive when replacing a windshield, it will fail when you need it most.

Wire wheel takes it right off. We use 3m window weld 08609. Put the glass in first. Run your bead between the cab(where the urethane was to begin with) and seal. Install the lock strip. Have clean up and towels handy in case any excess oozes out.

The stuff is black and like rubber or rtv. I couldn’t pull it out and didn’t need to go to bare metal, so I used a sharp chisel and carefully scraped the stuff off.

I didn’t have any pinchweld rust issues. But the interesting thing is the windshield gasket didn't have perfect 100% contact in all the circumference. The sealer they used definitly aided in sealing all the spotwelds, which were irregular and indented. Thank you all for the input! Great info. Now why don’t companies like LMC who put install videos on line use sealant?

Warren Lovell said:

Now why don’t companies like LMC who put install videos on line use sealant?

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Probably because it was not required way back when. Just the rubber seal was used originally, so that's what they show. That's my guess, anyway.

Precision weather strip products has videos, and more then once they say this is a dry install, use of a urethane caulk is highly recomended. I'm not sure on resellers like LMC, but most glass companies will refuse to do an install if they can't put the urethane in.

Use of urethane to retain the seal came out in the early 80s, probably because safety was becoming a big factor. This is why seat belts became mandatory (early squarebody from 73 to 77 or so, seat belts were an option) gas tanks move inside the frame rails, and finally glass was retained with just urethane.

Glass was probably installed with just urethane to speed production too, but like others said, there is a significant structural support through the glass.
If you do this, try to avoid putting a lot near the two bottom corner drain holes.

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