Sealing your windshield

[Da_Hose]

Hey everyone. I wanted to share something I worked on this weekend.

My windshield gasket seems to be leaking at the corners as it has shrunken up over time, and this weekend was the beginning of the big winter season rains here in Northern California. The leak has been particularly bad on the drivers side, but I don't want to replace the gasket as my glass has large chips in a couple places. I don't want to spend on replacing the gasket and glass, until I am ready for a re-paint. I also noticed that the factory manual says you should use sealant between body/gasket, but it looks like nobody ever put any in mine (which probably made the shrinking issue worse). End result is that I decided to seal the existing windshield gasket for now.

I have used many kinds of silicone to do many different jobs and I knew I didn't want to use that in this case. Nothing sticks to silicone, so if it doesn't grab or comes loose, there is NO fixing it. What I did find out, is that 3M sells a polyurethane adhesive called Windows Weld, that is specifically used to bond in a windshield. It's supposed to be CRAZY strong, so I tracked down a tube at my local parts supplier. Let me tell you that this stuff is NOT cheap, and it requires a caulking gun to use. It was $33 for a tube, but the adhesive seems to have done a beautiful job of sealing things up. We had really heavy rains over the weekend and the driver footwell is nice and dry. While there is plenty of sealant to do at least three windshield perimeters, I only need enough for one, so what is left in the tube will probably harden and I will have to throw it all away. I do wish I could buy it in smaller tubes. However, if you can wait on shipping, Amazon sells the stuff for $20.

https://www.amazon.com/3M-08609-Window- ... d+adhesive

If you need to seal up a new windshield gasket (or any rubber to body seal), I highly recommend this stuff.

Jose

[Finally6]

Good to know, because a windshield replacement is happening over the winter.

[Da_Hose]

In hindsight, I would suggest taping around the edge of the windshield gasket (nice and tight) with some wide, blue masking tape as well. That way, any excess sealant that squeezes out will come right off with the tape and you will have minimal cleanup to do afterwards. I used mineral spirits to clean up, by the way.

Jose

[v-wiz]

Good to know, did you lift the windshield gasket and fill in the sealant under the gasket?
Thanks

[Da_Hose]

Yep. I cut the tip at an angle, and slid it across, under the edge. Then I applied some light pressure evenly on the seal edge, to squeeze out the excess and get good contact. That's when it would have been awfully nice to have the tape in place.

Jose

[ron]

it. What I did find out, is that 3M sells a polyurethane adhesive called Windows Weld, that is specifically used to bond in a windshield.

Query? How do you intend getting the screen out next time?

This is what you should use as it never hardens.

Rav, The procedure outlined below will ensure your screens NEVER leak again.

viewtopic.php?t=21535&highlight=windscreen+sealing

Get your local windscreen shop to do it using this sealant.



To seal up your grommets use any black silicone sealant.

You can remove the mouldings before you remove the screen. Once screen is out, clean all old sealant from the rubber seal's many channels and then treat the seal with a rubber care product. Fit the seal to the new screen and then refit the mouldings (this is important as it is impossible to fit the mouldings with the screen in the car).

Install the complete assy. I then use a sealant gun with a tube of windscreen sealant (never completely hardens). Put the nozzle underneath the seal and apply the sealant between the body and the seal and between the glass and the seal around the complete circumference. Remove excess using a mild solvent and paper towel.

I have done 9 cars using this method and none have subsequently leaked.

HTH

[Da_Hose]

I see that type of compound used around the edges of windshields nowadays. They will use the polyurethane to bond in the windshield, then that soft stuff to seal all around the edges so water doesn't collect in low spots. I just replaced the top rubber strip on our 530xi and it had the soft stuff all along that top edge.

That could be a good solution, but it seems to me the real problem is that water gets under that edge at all. If you use the soft stuff, you have to make sure it is completely packed in there. Although I wonder if the shrinking I noticed in my windshield gasket would be reduced if it were adhered with the 3M stuff?

On to your practical question, Ron. On our 635's you are not really supposed to re-use the gasket. The manual recommends cutting the winshield out, or it can break. I would sacrifice a $150 gasket before good glass, so cutting it out is the way I would go. I think removing the left over adhesive should be pretty easy using one of those rubber decal erasers on the end of a drill. Although in my case, I think I will be doing a full body re-spray, which means I first have to remove the poor quality top spray a PO did somewhere along the way. All glass and seals will come off for that, so I was not worried at all about adhesive on the existing paint.

Jose