Installing 1966 Mustang windshield

Ivy66GT · 10-01-2009

Windshield installation time is almost here. I have installed several windshields with a rubber gasket where a cord in the gasket pulls the rubber lip over the edge of the sheet metal. I don't think I have ever done it on a Mustang but I generally understand how its supposed to work. My problem is that I read the shop manual directions on how to install the '66 windshield.

The first part I understand: shoot sealant into the gasket's glass groove with a caulking gun and install the gasket onto the glass. Then it says to lay more sealant "all the way around the body opening outer flange". Then you position the glass in the opening and work it into place with the pull cord starting at the bottom.

I understand that the 2nd groove in the gasket holds the pull cord so starting with sealant in that groove would be a problem; the cord would likely pull most of it out. But if the sealant is laid out on the sheet metal it seems that the sealant is going to stick to the outside of the gasket when you lay the glass into the opening. The sealant needs to end up down inside that second groove, not smeared all over the outside of the gasket. Is there a trick I am missing to keep the sealant where it belongs so it will end up inside the 2nd groove instead of as decoration all around the inside of the windshield?

I seem to remember shooting the sealant into the groove after the glass is mounted on the car but on a Mustang that doesn't look practical.

The Greek · 10-02-2009

I did the rear glass in a coupe that I used to have following that sealant application method. Needless to say, I had sealant all over the place, including me. It took longer to clean up the mess than the actual installation.

On a recent episode of "My Classic Car" they had a representative of a company that makes the gaskets for vintage cars. They showed the installation procedure using the cord. The rep. said that no sealer was needed. He strongly emphasized that the outer edge of the glass, where the gasket was in contact, was thoroughly clean. He also stated that the metal flange portion had to be clean and smooth. Then he and the host (Dennis Gage) installed the glass, placing the bottom portion onto the flange first.

The show's host once again asked about the use of sealer, and again he stated that as long as the glass was clean and the metal flange was clean and smooth that it wouldn't leak and no sealant was needed. This was news to me. I haven't tried it out, but I always wondered how the assembly line installed glass without any traces of sealer. They must not have used any either, but I'm still not sure on that.

The gasket was installed onto the glass first and the cord appeared to be 1/8" diameter double braded nylon. The next time I go to install some glass, I'm going to try this method. I'll never forget the mess that I had to clean up after using the recommended sealer.

The show has a web site or it can be sourced through a link from the "Speed Channel". They have segments posted on line and it may be there for you to see.

Ivy66GT · 10-02-2009

Thanks Greek. I can imagine the mess which is why I asked.

I re-read my BMW shop manual since I know I replaced both front AND rear glass in that one over 28 years of ownership. They do not use any sealant except between the glass and the gasket. The other groove just fits to the clean sheet metal. The difference here may be that the sheet metal flange on a Ford isn't smooth enough to seal well without sealant? I don't really remember the details of what the German sheet metal edges looked like. I don't recall that XK Jaguars use any sealant in that spot either.

On the BMW rear glass I had a problem in that the current glass is thinner than the originals. So the new glass wouldn't seal into the wider slot in the rubber. I ended up squirting lots of sealant AFTER the glass was in the car. I did get it to seal but the stuff kept squirting out for months afterwards anytime it would sit in the sun. I don't know about Mustang repro glass thickness but since this is an original windshield I won't have THAT problem.

Anyone out there have experience on how to get the Mustang glass installed without making a total mess with the sealant?

Sick467 · 10-02-2009

I can't speak for experience, but this is a good read...

Installing New Front And Rear Glass On A Classic Ford Mustang - Mustang Monthly Magazine

Ivy66GT · 10-02-2009

Thanks Noel. The method these guys used is interesting and may be the way I decide to go. I'll have to study it more closely. At least we all agree: the shop manual method will make a huge mess.

kevink1955 · 10-02-2009

You are right, the cord does pull the sealer out of the grove.

I did a 67 Windshield and rear window on a coupe about 2 weeks ago. I did the rear window using the rope method and made a real mess. When it came time to do the windshield I filled the grove with sealer and used a hook (cotter pin remover) tool to pull the seal over the body.

The hook tool worked fine and made 1/4 the mess the rope did. I already had the dash pad and trim installed and I do not think the rope would have gotten the lower part of the seal behind the dash trim. As it was I had to work with the tool to push the rubber behind the trim.

Ivy66GT · 10-14-2009

We got the windshield installed. Put sealer in the glass channel, then put the gasket on the glass. Then put sealer in the other channel where the metal pinch weld goes. Didn't use a cord but just set the glass in the opening. The best tool I could find to work the rubber over the pinch weld was my fingers which worked pretty good except at the two upper corners. They were difficult but not impossible to do with fingers. The mess wasn't too bad except on my fingers which weren't difficult to clean. Then we put a bead of sealer all around the outside of the gasket between the gasket and the body. Especially at the upper corners I think there would have been a leak without that extra sealer which Ford doesn't tell you to use. The link above shows guys shoveling on the sealer around the outside which I think is overkill. We didn't use nearly that much sealer on the outside, just enough to close the gap and then leveled it with my finger. We still used 1 1/2 tubes of 3M 8509 for one windshield.

Icerat · 10-19-2009

You really don't need sealer anyplace but on the mating lip where the weatherstrip lays flat along the windshield frame (not including between the windshield and the weatherstrip which is mandatory but not difficult). The sealer in the groove method is the easy and fast way to put sealer between the windshield flange and the weatherstrip. It is just as good to install the windshield with no sealer and then lift the outer lip and apply after. The trick is to do it once if you use the rope and want to use sealer in the groove. Fill the groove with sealer, spray the outer flange and the rope with cooking spray and install the rope with the starting point at the bottom in the groove. Wear rubber gloves. Have someone put slight pressure along the outer edges as you pull the rope around. Wrap the rope around your gloved hands as you go. The sealant won't get all over everything and the rope will pull out easily. I have done about 5 this way both front and rear and never had a problem or a leak.