[firebird_red]

GM used to install windshields and backglass with a tar-like rope bead seal between the channel and the glass. Then a butyl caulk sealed around the perimeter.

3M offers five different window kits for the rope bead. They are 1/4", 5/16" and 3/8" round or 5/16" and 3/8" rectangular profile.

Does anyone know which kit is correct? If the glass elevation is wrong from using the wrong rope, the moldings won't fit correctly. My question pertains to 67-69 camaro/firebird front and rear glass. I've heard front and rear kit might be different, but who knows?

Well, I hope someone here does, actually.

[MARTINSR]

“Basics of Basics” Window setting
By Brian Martin

First let me say that the information in these instructions was compiled after years of installing and repairing rusty and leaking window pinch welds. I feel that with what I have seen in failed, overly rusty window pinch welds, and where I have seen pinch welds that have remained in good condition gave me a good idea on what works and doesn’t work. The rust found in window pinch welds is many time directly related to how a window was previously set. These instructions I feel give the best seal and long lasting results. Let me say that there are a few different ideas on things, these have worked very well for me. This instruction is starting after any rust repair, primer/paint. That would require MUCH more instructions.

First off get some 3M (or there are other brands) "pinch weld primer." It comes in a little 1/4 pint or so sized can and has a brush attached to the underside of the lid. Remember, you only apply this over a very clean surface. You should have a clean painted or primed pinch weld. The “pinch weld” is the area where the window butyl tape actually sits. If you will notice that is where you will see the spot welds that hold the inner and outer pieces of that area together. These pieces are STRSW (Squeeze Type Resistance Spot Welder) welded and “pinched” together by the welder, hints the name “Pinch weld”.

Before you install the clips be sure they are correct!!! You should start with either new ones or VERY nice old ones. When they are installed the top of the clip should be just a hair below the top of the pinch weld or body surface. I also recommend that you trial fit a piece of the molding to see if it fits correctly. This is time very well spent. If you find later that the clips are wrong, you will REALLY wish you did this trial fit.
You could even set the window in on some rubber blocks and install the moldings to be sure it will all work well.

The Butyl tape will not remain the advertised size when the window smashes it down. So don’t think that the ¼” butyl tape will STAY ¼”. That is why the tape you use is larger than the actual space you will have between the bottom of the glass and the top of the pinch weld surface. ¼” Butyl tape (3M is one brand, there are others) will end up at about 3/16, 5/32 or even down to 1/8”. The 5/16” will end up at about ¼ or 7/32”. The 3/8” will be 5/16 or 9/32”. The butyl tape can be flattened more, if you get it warm enough. So these numbers are an approximate.

After you install the clips brush the pinch weld primer on the bottom of the pinch weld where the butyl tape is going to lay. Brush up around the clips good. The paint gets scratched when you slip the clips on to the studs and this primer will help protect it.

Next you want to set the window in the hole and find what rubber setting blocks you want to use. There are a few that come with the butyl tape kit and you set them different ways to make them higher or lower. Be sure that the window fits evenly all the way around. Run a piece of masking tape from on the glass out onto the body on the sides and the center of the top and bottom. Really only one should be needed but it helps to have more so you helper can see one well too. These tapes are then cut on the edge of the glass so you can remove the window again. Just leave the tape on the window and the body for alignment purposes.

Be sure the window is clean and free of residue of any kind. With it lying on its back, put the butyl tape on the edge of the glass without hanging off. Roll it out and as you go you can pull the paper off it so that way when you come to a corner you can get around it. If the paper is on, you can't get around the corner. But you want the paper on as you are going down the tops and sides to help you get it straight and so you don't touch it. At the point where they meet, run one next to the other and at the point they pass, cut it with a NEW razor blade. Then DON'T touch the tape, using the razor push it, blending it together. Most guys will tell you to make this joint at a certain spot like on the side or at the bottom. I really don’t think it matters as far as leaking, if it is done incorrectly it WILL leak, what does it matter where it leaks? The point is, do it properly and it won’t leak. I like to look at where it will be the least seen. On the sides it is usually seen and looks like hell. I usually make this splice at the bottom, it seems to be the most hidden spot. You can get the butyl tape in ¼”, 5/16” and 3/8” in diameter. I have found that the 5/16” is the most common with ¼” being used in late model cars on the quarter windows. The 3/8” is rarely used and can really get you in trouble. If you set the glass with the 3/8” you may find that it is impossible to install the moldings because the glass is too high!

NOTE! Some of the new (and replacements for older cars) windshields are thinner glass and the 3/8" butyl tape is needed to set the glass. It raises the glass up to make up for this. So, check with a good trial fit first! If you have an original glass DO NOT use 3/8” butyl tape it will raise the window up too high and the moldings will not fit!

Then with your helper set the glass in using the masking tape as a guide. DON'T LET IT TOUCH until you have it where you want it. YOU WON'T HAVE A SECOND CHANCE the butyl tape sticks RIGHT NOW and will not let go. If you have the glass a little over or up or down too much you can move it a LITTLE after the glass is lying in. Before you push on the top of the glass, using a plastic setting tool or even a piece of wood you can wedge it into the pinch weld channel and pry the window over, VERY carefully. At this time it is best to get it warm. If you can get it in the sun and warm up the glass and butyl tape and push on the top of the glass to get a good seal all the way around.

Now comes the real important part, sealing. First let me say that I have done many windows and used NO sealer what so ever. The Butyl tape alone should be sealing enough. But as an added "safety net" I do the following.

I take a plastic "bondo" spreader and cut it to about a half inch in width. I also round the corners with the razor nice and clean. Using a high quality urethane sealant I put a little strip right on the side of the glass edge or on the butyl tape it's self. Using the spreader I spread it down the side of the glass over the butyl tape to the bottom of the pinch weld, forming a seal from the top to the bottom vertically. In other words this sealer is covering the edge of the glass and the butyl tape, THAT IS IT. The sealer goes down to hit the bottom of the pinch weld right where the butyl tape is resting, but that is it. That bottom edge of the sealer where it hits the pinch weld is most critical. Be sure that it IS sealing down at the pinch weld. It should have a nice clean line as it hits the pinch weld. If it pulls up off the pinch weld, it is not a seal. Don’t assume because you have that sealer down in there, that it is sealed. If you put the bead of sealer in there and then spread it with the bondo spreader with pressure against the edge of the glass and butyl tape, it WILL flow down and seal the bottom, you just have to be sure you are doing that. DO NOT PUT THE SEALER ALL OVER THE CLIPS OR FILL THE CHANNEL this is a DEATH sentence to you job. When you are done, you should be able to still remove the clips if you wanted, that is doing the job right, no sloppy sealer all over the place just because the molding will cover it. Every little nook and crannie created by the sloppy sealer is a place where water will gather and sit longer than needed. This is a place for rust to start.

If you do this and you and see the seal has been made from the top edge of the glass down to the bottom, you know it will never leak. When water gets in there, it will be able to evaporate. If you fill the channel with sealant, the water gets in and can't get out!

You now can put the moldings on and off at your leisure. If your molding is giving you trouble and not clicking into place on the clip. You can take a rubber squeegee and place it on top of the molding and then a small block of wood and tap; JUST tap lightly on top and you can get even the most stubborn molding on. But if you trial fit them and didn't put sealant all over them this shouldn't be needed.

If your car has original glass, 5/16" if the windshield is new,3/8 would PROBABLY be needed. But check to be sure.

[firebird_red]

Martinsr, thanks for your very detailed reply. I hadn't thought to ask how to install the window and you answered that too. You've given me answers to questions I didn't know I should ask. Your hint to dry fit the glass and trim is sure to save me a lot of trouble.

I had arrived at the conclusion you're describing here, that too much sealant surrounding the glass traps moisture and encourages rusting. My window was removed by the previous owner who was evidently trying to fix leaking and rust issues. Who ever did the work completely filled the channel with butyl caulking. They didn't clean the steel to shiny metal and repaint either, so sealant was applied over already rusting metal over some portions of the "repair". The steel rotted beneth the caulking because it retained water directly on the steel. The rust propagated the entire length of the sealant.

The bottom pinch weld is oriented at such an angle that is forms a 'V'. After the car is rained on, that channel fills with water. This water remains there until is has a chance to evaporate. I was thinking this area could be improved by adding some drain lines much like some cars have for the sun roof channels. A drain from each corner would empty water that collected in the channel. They could be fashioned from flared tubing and soldered in the lower two corners. They would have to be maintained free of debris to work though.

I have a question about the steel pins that retain those molding clips. These pins (I describe them here for others reading and I'm sure you know exactly what I'm refering to) look like tiny box nails with a head. The clip passes over the head and is then pushed down a ramp until the clip locks in place. These pins contribute to the rust issue, along with careless installation that scratches through the painted pinch weld. My pins are long gone and were already replaced once with philips head screws designed for this sort of repair. They are well rusted or gone now.

These repair pins are offered in steel or stainless. However, either type screws through the body, thus opening up the pathway for water entry into the threaded connection. Do you believe the pinch weld primer your advising is adequate to seal this problem? Is there something more that should be done that would extend the life of the repair?

The bottom glass channel (pinch weld) has errosion in some areas that are perhaps up to 50% of the metal depth. There are a few holes to be repaired also. The remaining metal has adequate strength to support glass. Is it adequate to use normal filler, primer and paint to repair that surface? I suppose it could be leaded in, but I wonder about paint issues over lead compared with the intended paint substrates in this wet area.

[MARTINSR]

Originally posted by firebird_red

The bottom pinch weld is oriented at such an angle that is forms a 'V'. After the car is rained on, that channel fills with water. This water remains there until is has a chance to evaporate. I was thinking this area could be improved by adding some drain lines much like some cars have for the sun roof channels. A drain from each corner would empty water that collected in the channel. They could be fashioned from flared tubing and soldered in the lower two corners. They would have to be maintained free of debris to work though.

I have done the very thing to a couple of cars. My brothers 4 Riv was the first, it worked out very well. I used just as you suggested, a short piece of brake line with the flair. The one thing you have to remember is that you don't have to completely weld or lead something like that. The factory had seams that were filled with body caulking, you can do the same thing. I tacked the tube in with the MIG and then carefully sealed it with a urethane seam sealer just like you would use on the seams in your trunk floor for instance. I still see the car 20 years later and it is still working fine.

Originally posted by firebird_red
I have a question about the steel pins that retain those molding clips. These pins (I describe them here for others reading and I'm sure you know exactly what I'm refering to) look like tiny box nails with a head. The clip passes over the head and is then pushed down a ramp until the clip locks in place. These pins contribute to the rust issue, along with careless installation that scratches through the painted pinch weld. My pins are long gone and were already replaced once with philips head screws designed for this sort of repair. They are well rusted or gone now.

Again, I am of the same thoughts, they do contribute. After looking at those darn things rusted in window frames as well as simple side mouldings I think I came up with the reason. They shield the base of the stud from the primer and paint like a little umbrella, that is where they start rusting. I don't like the screw in studs as all. I have used the screw in clips with great success. You will find these clips on the side windshield posts from the factory on GM "A" bodies up thru 67 if I am not mistaken. I know without a doubt 64-65.

Originally posted by firebird_red
These repair pins are offered in steel or stainless. However, either type screws through the body, thus opening up the pathway for water entry into the threaded connection. Do you believe the pinch weld primer your advising is adequate to seal this problem? Is there something more that should be done that would extend the life of the repair?

Like I said, I don't like them. If you did use them, I would put a drop of seam sealer prior to screwing them in. And put them before you paint to try to protect them with paint as well.

Originally posted by firebird_red
The bottom glass channel (pinch weld) has errosion in some areas that are perhaps up to 50% of the metal depth. There are a few holes to be repaired also. The remaining metal has adequate strength to support glass. Is it adequate to use normal filler, primer and paint to repair that surface? I suppose it could be leaded in, but I wonder about paint issues over lead compared with the intended paint substrates in this wet area.

You don't want to do any filling there at all, unless it was lead. But honestly, none is needed. If he buytl tape doesn't go down into the craters the urethane sealant will.

By the way you could use straight urethane sealent and don't use the buytl tape at all. This is a lot trickier but could be done as well.

[bullheimer]

awesome info and thanks alot martinsr. i got the jar of primer. i dont have the urathane tho. i was really wondering about the thickness of the tape to use and you answered that question.

i thought the primer tho was for the channel, and you said, as to the directions, that it goes on the glass. but you also said it goes in the pinch weld area, so i am putting it there too

my mom's 70 cadillac has the rear window out now. i have to put it back in today (sat) or tomorrow as they finally discovered it here at work after 3 weeks. i have been airing it out because mass water leaked into the trunk/back seat area and mildewed/rusted just about everything. i dont have a garage for it at home so the glass has to go back in now.

around the edge of the channel "pinch weld" area has a rubbery like paint all around it already. that must be primer i take it. i can use that there like you said before and after i put the clips in, right? i'll re read what you wrote and probably get more out of it. thanks for having it there for us.
a couple of other things: you are NOT spozed to touch the butyl tape at all? what if you do? i just found out my tape is 3/8, so off to the store i go
one more thing for the complete idiot: with the tape around the complete edge on the galss, how ya pick it up and put it in?

[MARTINSR]

Well, first of all no where do I say to put "primer" on the glass, if I have said something that could be misunderstood please tell me where so I can rewrite that part. You want the glass CLEAN, with nothing on it.

It ONLY goes on the pinch weld area. And really, if it is repainted or something it is not needed.

The "rubbery stuff" around the window, I have no idea what it is. I would have to assume it is some silione or other sealent that someone has slathered in there. It really should be removed as it can trap water. But it is hard to say, if it is smooth and just looks like paint or something, you can probably leave it.

How do you install the glass without touching the butyl tape? Very carefully, that's how. Listen, if you touch it and don't mess it up or leave some grease or something on it, no big deal. WASH YOUR HANDS BEFORE. The biggest thing is that if you do touch it, there is a good chance you will really STICK to it and simply pull it up or mess it up.

You could also put the butyl tape on the pinch weld as well, then set the glass on it. The hard part about that is you end up with the glass hanging over it and it is hard to seal it up with the urethane. With the butyl tape right on the edge it is easy to seal it.

[bullheimer]

okay i think i got it on. the directions on the 3M primer said for use on automotive glass (and under "other uses" to put on the pinch weld), so i brushed some all around the outside of the glass after i cleaned it good with paint thinner. i used the 5/16 and i had some big gaps!!! i mean i don't think the 3/8 would have filled it! so i pushed and pushed and pulled some peices of butyl tape so they were thinner, cut with scissors and pushed into place where the gaps were. where i had a water leak before, were i didnt see a gap and didnt fill in, i did the same and filled in the gaps, just pushing in pieces of tape on top of the other. i then water tested again and it sealed! can i count on this to hold up? is it okay to do what i did stuffing more tape into gaps?
also, how much should i or could i put my weight on the glass to try to push it down? now that it's sealed can i forget it? god i hate being ignorant but this is my first windshield install

(just an aside here. i got the moulding all back on and everything. did a little more intensive water test and it turns out the water was getting into the trunk thru a bolt hole from a screw holding down the vinyl top trim. it rolled down onto the back fenderwell and into the passenger compartment filling up the floor and then the water condensed on the top of the entire trunk area causing rust. now it's all dry, but removing the window was probably a waste of time as the top has to be replaced.

[MARTINSR]

Honestly, I have never, ever seen a butyl tape not seal. I am wondering if you didn't push the glass down enough to form the seal. Was it warm enough? If the butyl tape is cold it isn't going to compress.

You would have to have some SERIOUS inconsistencies in the pinch weld to be bad enough where the butyl tape wouldn't work.

Is it going to seal? Your guess is as good as mine. I know you "could" do, but I have no idea how you did it so it is a little hard to know.

[bullheimer]

martin go thru my journal and you will see how i could F up a train wreck! i don't know why the gap was so big but it was. i test fitted the glass in w/o butyl tape about five times and never noticed it. i pushed and pushed. i stood on top of the trunk and put both hands on it, it just wouldn't touch. that's when i decided to pull off some more butyl tape and stuff it in all the gaps. i think it will hold, but like i said the vinyl top has to come off for me to leave it outside around here, there is rust showing thru it anyway-it's white. i poured a good volume of water over the whole car and no leaks from the glass whatsoever, i feel good about it...whatever that means. thanks for the info tho. i thought cadillac had better quality control over the way this glass fit in. i was suprised. there was not much rust, so no rusted away material to blame for the gaps. i also left the flat rubber stuff in place as well as it looked factory and i was afraid to pull it out

[MadRabbit]

I have this tube of stuff called NP-1 "one part polyurethane sealant"
that a window guy (windows in a 25 story building guy)gave me and said it would be the stuff I needed to put my new windshield in with.Has anyone heard of this stuff,and is it the stuff I need?I will be replacing my windshield in my 69 impala soon

[MARTINSR]

You really want to get automotive products. Sure that sealant may be the same or similar, who knows. But just because it is free doesn't mean it is a good deal. Go get yourself some 3M #8693 or 8609. These are "moisture cured" urethanes and designed for the job.

Urethaning in a window is not easy, I recommend the butyl tape if you aren't pretty confident with the urethane. It can be a VERY sloppy mess. I cut out and urethane windows in at work all the time on the collision jobs I repair, they all don't go smooth.

What you do is cut a "V" in the side of the plastic tip that comes with the adhesive. Cut the end off first, leaving a quarter inch or so hole in the end. Then cut the "V" ON ONE SIDE ONLY. With that "V" you can place the tip of the plastic right on the pinch weld and squeeze out a triangle shaped bead of urethane. You will need some blocks set here and there on the sides and top and bottom to set the depth. 3M makes foam tape you can use for a "dam" to hold up the glass. You will then set the glass on top of the urethane and press it down a LITTLE bit.

If you need something more detailed let me know.
Brian

[MadRabbit]

I will probably buy the butyl kit for my car and get the molding clips too.thanks for the help.I think I'll use this NP1 for something else I want my widows to NOT leak..

[MadRabbit]

I ordered my butyl and urethane ,molding clips and stuff to do my windows today...I will be reading this thread allot in the next week or so..

[roger1]

Question:

I am ready to install a new windshield in my 69 Vette. I have a new butyl tape kit and the urethane sealer. I stripped the pinch-weld down to bare metal, mig welded in a couple of patches for some small rust holes and primed the whole channel with SPI epoxy primer. Do I still need to apply 3M pinch-weld primer? If so, should I lightly sand the epoxy first? (I brushed the epoxy on and it is glossy.) My local glass shop said I could lightly sand the epoxy and use the butyl tape without the pinch-weld primer.

Thanks,
Roger

[MARTINSR]

The glass shop is right. Though, the sanding may not even be nessesary, I would say not.

That is actually the "legal" way to install a urethaned window in a late mode unibody car, the ONLY way you are allowed to do it is urethane over epoxy that was applied to bare metal.


Brian