Ok, I have to replace a cracked windshield and have been going through the archives about how to seal the thing and am a bit confused. I'm concerned about the windshield setting too low and the trim not fitting so I heard about 3/8" butyl tape but understand that's a no no because glass companies won't use it and it doesn't seal well. So I am looking at my AIM and trying to cross reference in threads about spacers and dams. What are the spacers, how thick are they, how many, spaced how far apart? and what about this "dam" thing (no pun intended). Where do you get this stuff? I had a glass guy come out to install and he had only tube type sealant and I had to stop before he got going because I didn't trust that process. Now after reading I'm probably more confused.
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Re: 70 Windshield installation help
Wayne -
The step-by-step detailed windshield installation procedure, including descriptions of the spacers and illustration of their location, is described in the "Corvette Body" chapter of the Chassis Service Manual. What we call the "dam" is called an "adhesive sealing strip" in the manual, and the tube your glass guy had is urethane windshield adhesive, which is the correct material. -
Re: 70 Windshield installation help
The technology for installing windshields has improved somewhat over the years.
Butyl tape will seal fine, but I think the Feds would allow it to be used only for side windows as early the eighties. A "dam" is used to maintain the sealant thickness under the glass and keep it from squeezing out into a big mess on the interior. Spacers are used to keep the weight of the glass from squeezing out the sealant and maintain proper sealant thickness under the glass. As John said, urethane is the "right stuff", and has been since at least the eighties (In fact, it seems like John may have been the one that told me that
).
Since your installer glues in a lot of windshields in a day, he's probably developed a few shortcuts over the years. For example, he probably won't even bother to remove your interior moldings, and he may think a little sealant inside is no big deal. How else can a guy make a buck coming out to your house to glue in a windshield?
It's tough being a perfectionist and a restorer...you have to learn how to do a lot of things you never wanted to learn.
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Re: 70 Windshield installation help
Also, as you read/study the AIM, you'll find the factory used a LOT of sealant components in MANY places other than just under/around the glass. You'll see sealant called out for the threads of the various screws used to hold the molding/clips, in various places under the top and side molding, Etc.
The situation is akin to the little Dutch boy with his fingers in the dike! Each use of sealant had its place in fighting water migration to prevent the birdcage's windshield surround from rotting. Few of the independent glass shops bothered to replace the factory original sealant(s) when they did a windshield R&R job...
So, now that you have the 'opportunity' to check things out with the front glass removed, TAKE the time to inspect and replace/refresh individual sealant(s) as required!Comment
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