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I have around .25" plus clearance between the trim and the glass and barely flush with the surrounding body metal. I would assume that the trim would be tight against the glass and overlapping the metal. Is this normal? This gap is around the entire windshield. Roofline Upper passenger side corner of the windshield
That makes sense. The solution appears to be finding a reputable installer for the glass who can address this with the correct sealing material. That is a heck of a lot of gap to suck up though, is there a gasket of some kind that is used between the glass and trim to address this? Regarding the gap between the trim and the sheet metal, such as the pic of the upper windshield on the passenger side, What should this look like? I unfortunately do not have a correct car to reference as a model and no prior experience to draw from for this. I almost have the body ready to get stripped and want to plan ahead on how to fix this if metal work will be needed.
What Joe said. My glass guy is a buddy, he told me for the trim to fit correctly he had to use thicker butyl tape because the new glass was thinner then the original.
I was looking up this butyl tape and came across a post on a chevelle website about windshield installation. Butyl tape was apparently not used at the factory? To correctly remove the gap I have, it appears that the idea is to apply urethane, then the installation of the trim squishes the urethane till the trim is snapped in place and no gap is present. I'm using the word "urethane" but it appears "Thiokol" was the sealant of choice at the factory. The post on the chevelle site quotes someone named John Hinckley, a long time GM employee with various rolls throughout his career it seems. Does the below sound legit?
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John Hinckley: "GM never used butyl tape or anything like it to install windshields or backlites. Period.
The body opening flange was coated with black silane primer using a flow-brush 30 minutes prior to installing the glass, and all the reveal molding clips were installed to the Body Shop-installed weld studs.
The glass was placed on a powered rotating fixture, inside edge up, retained by suction cups.
The glass periphery was cleaned using a solvent, dried, and a different silane primer was applied.
A fabric-reinforced self-adhesive foam rubber "dam" was extruded and applied to the glass just inboard of where the Thiokol adhesive would later be applied; the purpose of the "dam" was to contain any Thiokol "squeeze-out" so it wouldn't show from the inside past the edges of the interior garnish moldings after the glass was installed to the body.
After dam application, pumpable Thiokol adhesive (with a pyramid-shaped cross-section created by the dispensing tip) was applied adjacent to the dam, all the way around the glass.
Lower glass supports were fixture-located and screwed to the cowl, and rubber spacer blocks were glued to the opening flange. The spacer blocks set the height of the glass relative to the body to ensure a good fit of the reveal moldings.
The prepared windshield was removed from the rotating fixture, installed in the body opening, and pressed down against the rubber spacer blocks; wooden tonque depressors were used to "paddle" the Thiokol around the edges at a 45* angle from the top edge of the glass to the bottom edge of the body opening to ensure a continuous seal all the way around the glass.
Reveal moldings were installed.
That was the plant production process, and explains what is sometimes described as a "rope" being found when an original windshield is removed - the "rope" is the fabric-reinforced rubber "dam" that was applied prior to applying the Thiokol adhesive.
If you'll look in Section 4 ("Fixed Glass") in the Fisher Body Service Manual, you'll see exactly the same process for windshield replacement, except the "dam" wasn't included with the Service kit - masking tape was used instead to control "squeeze-out".
The Thiokol installation passed the Federal MVSS windshield retention tests, and contributed substantially to the body's torsional stiffness; it also helped the structure pass the roof crush test. It's illegal to replace a windshield with butyl tape, although some glass shops do it as a less-expensive short-cut method instead of doing the job right."
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Thiokol is a company. I should also point out that Thiokol made the solid rocket boosters that blew up in the Challenger accident.
The factory used urethane in a tube. That's one option. If you read the Fisher Body Manual, it shows you the process for applying the urethane and also the thickness. Maintaining that correct thickness without squeezing out too much requires some skill. The butyl tape is a substitute that's a lot easier and less messy. I've used the butyl a number of times with no issues.
Thiokol made the solid rocket boosters that blew up in the Challenger accident.
That entire SRB O-Ring fiasco was a complete CLUSTER PHUQUE. There were ~25 of us in a room in grad school watching it live. And, strangely enough, I reside in Beaufort, NC ~1/2 mile from Michael J Smith Field Airport (Michael's home town).
Part of the butyl tape debate revolves around which thickness butyl to use. I researched many forums/threads in preparation for doing both windshield and rear glass on my car and never could find a general consensus. Some said 5/16" with original glass...some said they always use 3/8". Others said the 3/8" was too thick and caused problems with correct install of the trim. Some said 3/8" only when installing new, thinner replacement glass. Read many stories of glass installers unfamiliar with older cars and their stainless/anodized trim setting the glass too deep using urethane and the trim wouldn't fit right. I'm sure the OP would love to hear more from those who have experience with this...as would I.
July 15th, 2020 | 09:59 PM
