How does sealing the glass to the gasket help to prevent leaks? I keep reading about doing it but I'm still clueless why.
My guess.... The theory is to keep moisture from wicking around past the glass and rubber seal. I also remember my glass buddy telling me some aftermarket gaskets don't fit very well.
Wow I just went back and read what I wrote earlier and I didn't go into much detail so I'll do that now. My old windshield leaked a bit and was cracked when I got the truck. My buddy who is a glass guy came by with a new windshield and gasket. The old windshield was urethaned in gasket to glass and gasket to windshield frame, drains full of it. All that sealant and it was leaking. There was some rust and pitting on the channel. He cleaned it up with a wire wheel painted it with a rust converter, then he went over the slightly pitted areas with I think like a glaze or filler, and then painted over that. Really the rust I had was not bad at all, he just said that if the frame is good and smooth and straight it'll seal up tight. He cleared all the sealant out of the drains too. He installed the new windshield & gasket with NO sealants of any kind and it has sealed up good for the last 3 or 4 years. He was at the shop for nearly 3 hours doing the job a good portion of that time was getting the channel prepped right and waiting for his paint to dry.
Short version from my glass guy, if properly prepped and installed in the truck with a good windshield channel no sealants should be needed.
My thought is If a guy is determined to use sealants at least make sure you don't fill the drains up with it.