Why Put Sealant Under Windshield Garnish Molding

[Larry M.]

I've read a lot of posts on installing both the front and back glass in a C2 coupe. Any while some say the front rubber gasket is all you need others disagree. And the assembly manual and service manual both discuss using sealant. The consensus seems to be 3M 08509. But what isn't clear is why you would put sealant on top of the rubber front gasket before installing the trim. What purpose it there? Is it just to keep the trim from rattling or is it supposed to be a water barrier in some way?

[Gary S.]

Re: Why Put Sealant Under Windshield Garnish Molding

To keep it from leaking. I have owned a zillion C2 coupes and never remember one without it. Here are two pictures of original paint coupes I owned showing the sealer. And the goop went full circle on the windshield...and was not real pretty. Red is a 65 and blue a 67.

[Joe R.]

Re: Why Put Sealant Under Windshield Garnish Molding

GM had a crazy idea that if you didn't seal the water out the metal frame around the windshield would rust away. And some did anyway!

You think they may have been on to something?

JR

[Bob R.]

Re: Why Put Sealant Under Windshield Garnish Molding

I installed a new window in my 63 and didn't think the sealant was necessary. At the national in Rhode Island in 2016 I parked the car on the field and it sat in a heavy rain for an hour or so wasn't driven just sat there. I had an inch of water on the carpet so I think the sealant is necessary. After the national I took all of the moldings off and put some sealant around the perimeter. I haven't been in the rain since so I can't say what will happen now but I'm sure it won't be that bad.

[James W.]

Re: Why Put Sealant Under Windshield Garnish Molding

If the sealant was applied to the molding, wouldn't this become a water trap and any water that did find its way into the channel under the molding would have no way out? I guess how would it drain?

James

To keep it from leaking. I have owned a zillion C2 coupes and never remember one without it. Here are two pictures of original paint coupes I owned showing the sealer. And the goop went full circle on the windshield...and was not real pretty. Red is a 65 and blue a 67.

[Mark E.]

Re: Why Put Sealant Under Windshield Garnish Molding

If the sealant was applied to the molding, wouldn't this become a water trap and any water that did find its way into the channel under the molding would have no way out? I guess how would it drain?

James

If water could get between the sealant and molding, that could be a future corrosion problem. I guess the tip is to apply sealant in a manner that prevents this.

I suspect GM was more concerned about leaks (a warranty risk) than rust (a problem after the warranty). Hence the sealant.