Converting Older Windshield Installations
I belong to several glass related technicians’ groups on Facebook and enjoy participating in discussions when I can. This past week a conversation brought back memories of my installer past and the old DW837/836 windshield. I thought I would share it with my readers this week.
The DW837/836 windshield is the windshield for a 1975-1991 Ford full-sized van. Back in the day, we used to do a LOT of them. That was our service vehicle when I was an installer. It has four-sided heavy chrome mouldings and a block size of 34×73, which makes it a large and awkward piece of glass to set by yourself. The original equipment adhesive was butyl tape.
When I did these windshields, we used round butyl to replace them. I would smear some liquid butyl on the passenger side bottom pinchweld and apply the butyl tape to the glass. Then, I set the glass onto the liquid butyl, slid it to the far pinchweld, set it in place, decked it and then back sealed the seam with a flow-grade sealant. This was a successful method because we rarely had a leak or noise complaint. The two types of butyl meshed together and sealed permanently.
Our Industry Standard says:
8.4 Whenever OEM retention systems are modified on later production models without body style modification, the most current retention system shall be used in the replacement unless otherwise specified by the OEM.
However, the Ford van never had a change to urethane until the body style changed in 1992. Thus, the OEM specifies butyl for a Ford Van of that body style so by rights, butyl could be used.
Today our industry recommends the use of urethane when replacing these parts, rather than continuing to use inferior bonding adhesives. This is to ensure the bonding is improved and not hindered and so the replacement must be done correctly.
One of the biggest challenges for field techs is that urethane and butyl are not compatible for bonding purposes. This means ALL of the butyl must be removed for proper bonding. Unfortunately butyl tape is difficult to remove, especially if the tape is older. You then must scrape off the biggest share, and continue with one of the following to remove the rest without damaging the paint:
- Use a sharpened plastic stick to scrape off the remainder of the tape.
- Use a big ball of old butyl to stick to the remaining butyl and peal it off.
- Use a solvent for removal. This would require an additional process to neutralize the solvent.
In any case, it’s time consuming and difficult to accomplish.
In a past posting I suggested the use of a tool used by collision centers to remove decals and pinstriping, called an eraser. It’s a rubber wheel inserted into a drill and used as a butyl eraser; it works well. It literally erases the butyl like pencil markings from paper without damage to the paint. The tech then dusts the pinchweld of rubberized residue, primes the pinchweld, applies the urethane to the proper height and width and sets the glass using the modern setting tools or a helper.
This method of butyl removal is fast, easy, economical and damage free. If you give it a try you won’t be sorry.