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914World.com _ 914World Garage _ Windshield install with butyl - is butyl primer needed?
Posted by: Kansas 914 Jun 23 2017, 07:41 AM
I have brand new paint on the car. I remember the last time I had a windshield installed by I don't think the installer used primer.
Is it best to prime the frame first and is butyl primer the right stuff?
Like this? https://www.amazon.com/CRL-Pinchweld-Primer-Butyl-Tape/dp/B000KZUZZK/ref=cm_cr_arp_d_product_top?ie=UTF8
Posted by: 76-914 Jun 23 2017, 07:48 AM
I did not use any however I did prep with Lacquer Thinner to remove any grease/oils. 
Posted by: Mark Henry Jun 23 2017, 08:00 AM
What size is the correct butyl...it's the tape right?
And is it the same for the rear window?
I have to reseal my rear window, looks like a rubber seal, but that's just butyl tape gone hard , I'm I correct on this?
Posted by: mepstein Jun 23 2017, 08:07 AM
What size is the correct butyl...it's the tape right?
And is it the same for the rear window?
I have to reseal my rear window, looks like a rubber seal, but that's just butyl tape gone hard , I'm I correct on this?
Yes, butyl tape on the rear
Posted by: Mark Henry Jun 23 2017, 08:09 AM
What size is the correct butyl...it's the tape right?
And is it the same for the rear window?
I have to reseal my rear window, looks like a rubber seal, but that's just butyl tape gone hard , I'm I correct on this?
Yes, butyl tape on the rear
Thanks Mark...another job for the list.
Posted by: Kansas 914 Jun 23 2017, 08:11 AM
What size is the correct butyl...it's the tape right?
And is it the same for the rear window?
I have to reseal my rear window, looks like a rubber seal, but that's just butyl tape gone hard , I'm I correct on this?
Yes, butyl tape on the rear
I used 5/16" 3M Windo-Weld available from Amazon. https://www.amazon.com/gp/product/B000CQ4AOE/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
5/16" (8mm) is correct for the front as you need to make sure the "chrome" trim snaps into place. I have heard horror stories about using 3/8". The manual says 5/16" (8mm) for rear glass as well but it is not as critical since there is no trim.
Posted by: Dave_Darling Jun 23 2017, 09:24 AM
Using the primer is not necessary, but it does help the butyl to grab better.
--DD
Posted by: Perry Kiehl Jun 23 2017, 09:35 AM
Butyl primer will improve the seal. For $17 more, why wouldn't you use it?
Posted by: Kansas 914 Jun 23 2017, 10:45 AM
Butyl primer will improve the seal. For $17 more, why wouldn't you use it?
Cheap insurance and this car will be a driver not a queen.
Thanks!
Posted by: Mikey914 Jun 23 2017, 02:39 PM
no primer required
New paint not needed for sure.
In stock
Have a set of instructions on site
http://shop.914rubber.com/Butyl-Cord-95mm-x-15-91-BR.htm?categoryId=-1
Rear glass kit with setting blocks
http://shop.914rubber.com/rear-window-reseal-kit-914RWK.htm?categoryId=-1
Posted by: bbrock Jun 23 2017, 05:58 PM
With luck, I'll be facing this task in the not too distant future. Other than originality, are there reasons to stick with butyl instead of moving to a modern urethane seal? 
Posted by: Perry Kiehl Jun 23 2017, 09:10 PM
Butyl tape is a consistent thickness, in this case 5/16", which is required to get the windshield trim to attach properly.
I haven't installed a windshield in over 10 years, but I think the urethane doesn't come in a cord or tape, it's in a tube.
What I like about the primer, in addition to the fact that the butyl adheres and seals to it better, is it "paints" the windshield recess black, so you don't have edges of Saturn Yellow, or Marathon Blue (or whatever color your 914 is) peeking out from around the windshield perimeter
Posted by: Montreal914 Jun 23 2017, 09:45 PM
For the rear window, I have used 5/16 butyl about 6 years ago. No issues. I had removed all traces of the original adhesive and degreased the paint with alcool. Nice fresh surface.
You want to use electric tape on the lower cabin side of the window to hide the butyl.
While in there, I remember replacing the rubber lip (914 rubber) that reach over the engine lid
Good luck.
Posted by: Dave_Darling Jun 23 2017, 10:07 PM
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
Posted by: bbrock Jun 23 2017, 10:49 PM
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
Makes sense. I've installed two 914 windshields many years ago and the butyl also seems like it would be easier, but no direct experience with urethane. Just wondered if there was any advantage. I like the idea of sticking with what's familiar.
BTW, on the two windshields I did, one was done with and the other without primer. I definitely preferred the primered install for all the reasons already mentioned (better stick, and leaves a nice black welt).
Posted by: stevegm Feb 11 2020, 07:22 PM
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?
Posted by: 914werke Feb 11 2020, 08:18 PM
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
I can attest that is the case...
Fortunately this is a DIY job,
Helps to have a buddy cuz you have one shot to stick it in the correct position.
On windshields youd be hard pressed nowadays to find a shop that will put one in with Butyl
Posted by: ConeDodger Feb 11 2020, 08:30 PM
I did this alone but another set of hands would be good. I used butyl and primer. Didn’t cost that much more to do it right. I’ve been around here long enough to hear a few horror stories about cracked windshields because of the modern goop. The shops were even claiming butyl wasn’t legal in California anymore. Not true.
#1 thing to do “while you’re in there” so to speak. Replace the forward vinyl behind the dash. Given the 914rubber.com dash board quality, you should do that too...
Posted by: lierofox Feb 11 2020, 08:32 PM
https://www.amazon.com/gp/product/B00473W5V8/ref=ppx_yo_dt_b_search_asin_title?ie=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.
Posted by: bbrock Feb 11 2020, 08:55 PM
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.
Posted by: stevegm Feb 11 2020, 09:10 PM
https://www.amazon.com/gp/product/B00473W5V8/ref=ppx_yo_dt_b_search_asin_title?ie=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?
Posted by: stevegm Feb 11 2020, 09:11 PM
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?
Posted by: bbrock Feb 11 2020, 09:36 PM
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.
Posted by: stevegm Feb 11 2020, 09:55 PM
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/B000CQ4AOE/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
I’m also getting the primer:
https://www.amazon.com/3M-08682-Single-Step-Primer/dp/B00473W5V8?ref_=mw_olp_product_details#immersive-view_1581478380133
Posted by: porschetub Feb 12 2020, 01:04 PM
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
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.Posted by: lierofox Feb 12 2020, 01:06 PM
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.
And here's the windshield frame, similar cleaning treatment was given with alcohol.
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.
Use the spacer blocks and preferably a buddy to help you guide it into place.
Posted by: mepstein Feb 12 2020, 01:20 PM
The warmer the better. Mark / Mikey explained the original butyl strip had a thin wire in it to heat it up.
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