Windshield install with butyl - is butyl primer needed? Options

[stevegm]

https://www.amazon.com/gp/product/B00473W5V...=UTF8&psc=1

I used this stuff to primer my windshield and frame.

Buddy of mine was the son of an auto glass guy so he helped with installing dozens of them over the years. Primer every time or it'll eventually begin to leak. I think he mentioned that it also helps provide a bit of extra protection to the butyl since it helps to mask the sunlight, in addition to the glass blocking the UV.

From what I understand, modern urethane adhesives, when they grab on, hold on WAY too well and the windshield becomes a structural/shear member of the car, and all the flex ends up being transferred into the windshield glass, which the 914 windshields were never designed to be used for, causing them to crack.

So you just put the primer on the windshield channel on the car where the butyl touches? As well as on the windshield?

[stevegm]

914rubber’s kit is 9.5 mm, which is 3/8”.

I have also heard 5/16” is correct, which is 7.94 mm.

Does anybody know which is correct? I want to use stock windshield trim. Has xx anyone used either size with chrome?

The factory manual specs 8mm butyl for both front and rear glass. Despite having a fresh 3/8" 914Rubber kit on hand, I bought 5/16" rope for the rear and it worked perfectly. I will use the same when I do the windshield.

Where did you find the 8mm butyl? Locally?

[bbrock]

914rubber’s kit is 9.5 mm, which is 3/8”.

I have also heard 5/16” is correct, which is 7.94 mm.

Does anybody know which is correct? I want to use stock windshield trim. Has xx anyone used either size with chrome?

The factory manual specs 8mm butyl for both front and rear glass. Despite having a fresh 3/8" 914Rubber kit on hand, I bought 5/16" rope for the rear and it worked perfectly. I will use the same when I do the windshield.

Where did you find the 8mm butyl? Locally?

I bought 5/16" butyl which, as you said, is very close to 8mm. My local FLAPS had it but it was about half the price on Amazon.

The factory manual also says to coat the outside of the windshield about 15mm wide with primer.

[stevegm]

914rubber’s kit is 9.5 mm, which is 3/8”.

I have also heard 5/16” is correct, which is 7.94 mm.

Does anybody know which is correct? I want to use stock windshield trim. Has xx anyone used either size with chrome?

The factory manual specs 8mm butyl for both front and rear glass. Despite having a fresh 3/8" 914Rubber kit on hand, I bought 5/16" rope for the rear and it worked perfectly. I will use the same when I do the windshield.

Where did you find the 8mm butyl? Locally?

I bought 5/16" butyl which, as you said, is very close to 8mm. My local FLAPS had it but it was about half the price on Amazon.

The factory manual also says to coat the outside of the windshield about 15mm wide with primer.

Thanks. I found this on amazon:
https://www.amazon.com/gp/product/B000CQ4AO...=UTF8&psc=1

I’m also getting the primer:
https://www.amazon.com/3M-08682-Single-Step...w_1581478380133

[porschetub]

Other than originality, are there reasons to stick with butyl instead of moving to a modern urethane seal? (IMG:style_emoticons/default/confused24.gif)

I have heard reports that the urethane does not give as much as the butyl does, and windshields tend to crack more easily when installed in our flexy fliers with urethane than with butyl.

No experience myself, but I used butyl on my car and it is holding up well.

--DD

(IMG:style_emoticons/default/agree.gif) have read the same thing,makes sense for the era of this car,most cars back then had screens held in a rubber and trim filler strip.

[lierofox]

So you just put the primer on the windshield channel on the car where the butyl touches? As well as on the windshield?

Yep! We did it back in 2017 (and no the car hasn't gotten any prettier since then)

Here's the windshield itself, cleaned and scraped and wiped as spotless as possible with ammonia free cleaner, alcohol, and finally dried before the primer was applied.
(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-18880-1581534405.1.jpg)

And here's the windshield frame, similar cleaning treatment was given with alcohol.
(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-18880-1581534405.2.jpg)

Work slowly and CAREFULLY when pressing it into place, especially around the corners to avoid cracking, should look something like this when it's all set in place.
(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-18880-1581534406.3.jpg)

Use the spacer blocks and preferably a buddy to help you guide it into place.

[mepstein]

The warmer the better. Mark / Mikey explained the original butyl strip had a thin wire in it to heat it up.