I am getting water in my cab, I want to seal around the window, my plan is to strip the rust, treat the metal, then seal with urethane, can anyone suggest what to treat the metal with before using urethane ?

 

Remove the windshield. Clean up/out the rust. Weld up holes. Coat with rust anihilator type product, any body ship supply place will have it, paint, reinstall windshield. What you can see there is the tip of the iceberg I bet.

:wabbit2:

 

Wabbit is right. I had similar rust on my '85, repaired that rust using a similar method to what you're talking about, and it still leaks. I'm going to take it to a professional body shop to do it the right way.

 

I've fixed this issue on multiple vehicles without recurrence, for up to four years and counting at this point. First pull all the trim around the entire windshield, then scrape all loose rust using a screwdriver and run a rough sandpaper thoroughly over it. If you need to paint any areas make sure they're extra clean. Blow out the joint and treat with phosphoric acid per directions on bottle (or as a second choice, any phosphoric acid containing primer).

If you can't cover the entire affected area with caulking and need to paint, follow acid treatment with primer and paint. Let dry and then masking tape both sides of the joint all the way around the windshield and fill with Dow Corning 795 silicone sealant. This is not your typical hardware store caulk, it is professional glaziers sealant and makes all the difference - does not shrink or oxidize at all and has unsurpassed adhesion and flexibility. It's sold by industrial supply stores, or online at Amazon, not cheap, but worth it unless you want to do this every year. Finally, tool the joint with a plastic putty knife, and throw away that worthless, water-holding trim.

My windshield, before cleaning up the joints after it dries -

 

Thanks for the replies everyone, I think I will do jb,s method. questions: the shop that put in the last windsheild used urethane ( so they said),after I strip the rust and treat with ospho( I beleive that is the same as what you recomend) do I fill with the silicone you suggest or do I paint first then put silicone and do you know if the silicone will bond to the existing urethane? Yeah I would rather not pull the glass at this point, seeing as it is sound. Thanks for the help!

 

DC 795 silicone will bond to any clean surface including urethane, as will any other silicone sealant to a lesser degree. You don't need to prime, as long as ALL the rust is covered. If you can't cover it all with caulk and think you may need to paint, prime and paint first, because no primer/paint will bond to silicone. If you try to paint after caulking, you will soon have rust that starts at the paint/caulk border and spreads underneath, undoing all your work.

 

Thanks Jb, I will be sure to post some pics.

 

So I wire wheeled around the windshield, treated the rust, with etching, por15, paint then dow795 silicone , great no leaks, except, I neglected to protect the windshield, must have just tapped the edge with the die grinder, yes it is cracked. We have annual safety checks here so I will have to change it now.

 

There goes another $15 tube of caulk Best fix for that is to find a back roads shop that doesn't care. As you can see in my old pic the windshield in that truck has been cracked since I bought it, and we have annual checks here too. A "good" mechanic makes all the difference...

 

it is against federal law to mount any windshield thats driven on the road with a silicone based adhesive, fyi. liability is the new way of life here in the states if any thing was to go wrong you can and will be held acountable, even among friends, liability is a fact of life no-a-days. just sayin, not looking to argue with any one. repair / treat rust and use an agrss approved urethane per manufactures procedure. (25 yrs in automotive glass industry) agrss= automotive glass retention safety standards

 

OP was wanting to repair without removing the original urethane, I was suggesting DC 795 because it is the ultimate, easy to use, leak stopper.

But since you bring it up... Where did you come by this information? Not looking to argue either, and not saying that I would put it past our regulatory agencies to pass a, or many, ridiculously misguided law(s) but good silicones are a far superior product. Whenever you're passing under a flush glazed skyscraper with 400+ lb pieces of glass for 500 vertical ft above you, you can bet they are partially or completely held in place with silicones. Structural engineers may spec small fasteners to hold glass in place while silicone sets for the longer curing product lines, but a heel bead does the grunt work for decades to come. Urethane is never used in commercial glazing applications, which would put a lot more lives at risk than auto glass if they failed...

One caveat, because of the longer cure times of single part products like 795 and 995, you'd need a secondary adhesive like glazing tape to hold the windshield while it set, or not drive it for a few days. There are many two part silicones as well, DC 982 and 983 for example, which are commonly used to glue lites of insulated glass together and seal out moisture and set up in under an hour.

I could understand regulating tensile strength, and I wouldn't use anything I bought a Home Depot to install a windshield, but I'd trust any of Dow's silicones with my life. Millions of people do every day whether they realize it or not.

 

Thanks jb,a shop down the road did pass me actually, maybe they will pass me again.

 

Thanks for the input lobu, I don't see the problem with using silicone myself.

 

Thanks for this info, jbtvt. Yes, I've heard of silicone used for high-rise glass. So that's it huh?

I agree with using silicone to thoroughly fill gap. Superficial trim only catches and retains dirt and water and hastens rusting (see illustrations on my post)

Guys,
I also stressed my glass so it cracked. My plan now is (post here):

1. Remove old windshield,
2. Fix rust spots properly with rust converter, etc and repaint
3. Have replacement windshield professionally-installed with low-profile rubber trim (shown on my post),
4. Fill gap with DC 795 silicone

 

I'm wary of any rubber around my glass nowadays, but the edge protection you mention is an advantage and it is certainly an improvement over stock. I wonder if the shop would let you back there to squirt a bead of sealant around the edge of the glass right before they put the gasket on. Then there'd be no chance of a path for water to work its way behind the joint. If there's one thing I've learned in 7 years of building skylights it's that water is one crafty SOB when it comes to weaseling into places you don't want it to be!

 

Lobuk does appear to be correct, BTW - http://www.agrss.com/documents/standardattachA.pdf and technically, it seems you're not allowed to even stop water leaks in a urethane sealed windshield using silicone!

To compare, Dow's urethane windshield adhesive is 700psi tensile strength vs 45psi for 795 and 350psi for 995. I tell ya, for as much of a struggle as it is to cut free a heel bead of 795 say nothing of 995 I wouldn't think you'd need any more, but they must have their regulatory reasons. So don't glue your windshield on with one part silicones, and if you do, don't sue me, I warned you

 

Tnx for all these inputs, guys! I observed the Safelite tech as he installed everything. I think he did an excellent job, is very personable and helpful. Below he put a thin bead of urethane adhesive at interface between rubber and glass. That would be further filled with adhesive as the good size main "V" bead he put squeezes out.


Re Silicone:
I got DC 995 but at last minute, I mentioned it to an aircraft mechanic friend. He mentions what could be the good technical reason for not using silicone as windshield adhesive. It is not about lack structural strength, but about a solvent or other substance in the silicone that I believe is acidic- Good for glass but not for metal.

So I guess now I'll need to research where to find exactly same urethane adhesive that the shop uses to fill that gap.

I will research more and add to my Windshield Trim Delete Post

 

The Cheap Silicone Is Acetyl-Oxy Cure (Acetic Acid Like In Vinegar) But This Disperses After Curing. 795 And 995 Have No Acetic Acid.

Edit: Phone autocaps every word on some sites, this being one of them. Just checking up it appears the correct term is acetoxy, no acetyl. You can smell this as soon as the caulk is exposed to air it smells like vinegar. 795 and 995 are safe on steel as are most higher end silicones from GE etc. If you want to avoid silicones entirely you could look into polyether sealants like M1 from Chemlink which also have excellent adhesion and toolability, they just don't flex as well.

 

Makes sense about the cheap one.

Nice!
I got the DW995 because it says structural sealant, but I haven't looked at it's composition/specs yet so it's good to know from you, jbtvt

 

Finally got the windshield in, had a company do it, 330$ glass included, they came to me as well, I did the prep with polyester resin and fiberglass.