Windshield Sealant..........

KTL · 05-11-2003, 05:59 PM

I thought i'd get the urethane sealant since that's what new windshields use. Let's hope it sticks good? As long as it keeps the water out, I don't really care. So, which windshield sealant to use when sealing your new gasket?

Not the high viscosity stuff!!!!

That stuff is thick! You have to squeeze like a mutha to get this stuff to come out of the tube!!!! I broke three cheap caulk guns with my kung-fu grip and had to go to The Home Depot the next day and get the "professional grade" gun for $13.

It was the pro gun (not pictured) that busted the tube open.

I had to cut the tip kinda small because a large bead is not needed for sealing the gasket to the glass and the body. WTF? I can't believe the tube broke open.

So I had to drop everything and go get raped ($12) for another tube of sealant. Got the lesser viscosity Windo-Weld kind and it worked much better.

Word to the wise. Have rubber gloves, plenty of paper towels, a blanket on your hood, a handy dental tool to remove the excess and help insert the tip under the gasket, and most importantly some adhesive solvent handy when doing this job. It can get messy in a hurry. A BIG hurry.

So, I highly recommend using masking tape around the gasket before you start. Make things much much much easier to clean up!!!!

Formerly Steve Wilkinson · 05-11-2003, 06:09 PM

The reason you had so much trouble is that those are all the wrong sealants. In fact, they're not sealants, they're essentially "windshield glue," which indeed is what is used when putting in a modern (i.e. not an '87 911) windshield. You should have used the vastly less troublesome, vastly more effective 3M product Window-Weld Resealant, which is what a good bodyshop supplier would have advised you. Goes in very easily, cleans up simply with any good pre-paint silicone cleaner.

Stephan

KTL · 05-11-2003, 06:29 PM

The only trouble I ran into was getting the high visc. stuff to exit the tube. Maybe you use a powered gun for this stuff? I dunno. I'll tell you that it ain't because i'm not strong enough. That's for sure. Other than the high visc. issue, the job was simple. And I figured urethane would serve as a sealant and an adhesive. Resealant seems more well suited for existing condtions, not new installations?

I didn't just pick this stuff of the shelf somewhere. I did do a bit of checking around to finally decide on the urethane. We'll see how it works. As long as it doesn't leak, that's all that matters. Some DIY'ers make the mistake of not bothering to seal the gasket at all!

Clean up of the urethane is no more difficult than the resealant.

Where were you when this question came up in past topics?

Silveresrty911S · Silveresrty911S's Garage

KTL,

Did you puncture the membrain that is inside the caulking tube, Most of the painting style caulks don't have them but all the silicon (expensive) do have the small section of aluminum inside the tube to keep it from dring out. I've seen alot of cheap guns get destroyed if you don't puncture the inner seal.

KTL · 05-12-2003, 05:00 AM

Rick,

Yep. I did puncture the thin alum. seal at the end of the tube. The high viscosity stuff is quite thick. It comes out of the tip like a sticky rope of rubber.

You're definitely right that the first three guns were cheap. Just flimsy sheet metal guns. Ah well. If nothing else, the job forced me to buy a good quality caulking gun!

I'll know better next time to use a different sealant. Although I don't think the urethane is going to cause any problems. It dries to a firm rubber when it cures. It's kinda like pouring liquid rubber in the channel to fill the void between the seal and the body. We'll see..........

Formerly Steve Wilkinson · 05-12-2003, 06:02 AM

Just hope you don't ever have to remove the windshield, because you'll have to break it, now that you've glued it in place. the reason they use these glues on modern windshields is that the windshield is a crucial part of the passenger-side airbag system--something that even a lot of glass-replacement shops don't understand. If the rightside airbag deploys, the windshield is intended to hold it in place and direct it toward the passenger. If the inflating airbag simply pushes the glass out--as it would if early-'80s 911s had airbags--it becomes useless.

The 3M Window Weld goes in easily enough, by the way, that I use hypodermic syringes with the needle removed, which still leaves a fairly small opening in the plastic or glass part of the syringe. Simple thumb pressure squeezes it neatly into place and hardly any even leaks out past the gasket.

Stephan

Superman · 05-12-2003, 06:17 AM

Yep. New car windshields are glued in place, and that is what you've used. Notice the WIDE black patch around the edges of modern windshields? To keep the sun off the glue, and to provide a WIDE glue patch. Modern cars get much of their rigidity from the glass, which is now a structural component.

The stuff I use under rubber seals (old style windshield systems) is called Glazing Compound. It remains soft. Does not dry. And I get it warm before I use it.

Oral surgeons hand out these syringes with long, curved plastic 'needle' noses, for patients to use to irrigate tooth areas after an operation. They also make EXCELLENT applicators for glazing compound.