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Amazing mystery windshield sealant

Discussion in 'The Hokey Ass Message Board' started by Kustomkarma, Jul 12, 2009.

  1. Kustomkarma
    Joined: Mar 31, 2007
    Posts: 898


    Now that I've got your attention, here's my question. I recently reinstalled the windshield in my '64 Mercury Comet without using any kind of sealant (these windshields mount using a gasket like an early Mustang or Falcon.) Now I'm wondering if I should have used something to prevent leaks. I've asked around quite a bit and I always get different answers on what to use. Some people say 3M Window Weld, some say don't use anything, some say electrician's putty, etc. etc. Even the glass places I called don't know. I have been told that there is some kind of mystery sealant that comes in a tube and is non hardening (flow grade butyl rubber?) that would do the job. I would like to be able to remove and reinstall the windshield again if I need to without destroying the gasket or paint on the car. So does anyone know what the name and brand of this fabled substance is?
    Fry likes this.
  2. plywude
    Joined: Nov 3, 2008
    Posts: 700

    Member Emeritus
    from manteca ca

    I was in the glass industry for 40 years, I never saw any glass that was wrapped with rubber sealed with any sealant, the rubber gasket should be tight enough to keep water out, that is the way it was designed .........:D
  3. Kustomkarma
    Joined: Mar 31, 2007
    Posts: 898


    Thanks for the reply. Anyone else got an opinion on this?
  4. I agree with Plywude, in the panel shop I worked in the glass guy never used anything other than the rubber gasket.
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  5. TagMan
    Joined: Dec 12, 2002
    Posts: 6,028


    I had a "37-'38 GM Fisher Body repair manual that described and pictured the rubber gasket on those cars being sealed with a sealant in a tube. There was a special tool (kind of looked like a calking gun, but not as bulky) they used and used a GM name / part number for the sealant.

    I installed new glass & gasket on my '37 Chevy coupe several years ago and it leaked a bit in heavy rain. I took it in to a local auto window glass shop and he used a non-silicone sealant for around $30. I haven't had a leak since.

    I seem to recall that Eastwood does or used to sell a non-silicone glass sealant, too.
  6. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,965

    Shifty Shifterton

    Don't seal it unless it leaks. If it leaks you really need a new gasket, but if you're bucks-down and working on a beater, I've goobed sealer to avoid buying a new gasket.

    The thing to watch with sealers is the type of gun required. Many of them require a direct drive caulk gun that's different/stronger than the one you use around the house. And depending on the vehicle, a tube of high end sealer can almost equal a new gasket.
  7. ccain
    Joined: Jun 13, 2009
    Posts: 343


    I just removed the windshield from my 64 Fairlane Wagon... The windshield had a "Carlite" marking and the gasket had cracked to reveal gaps, some up to 1". So, I'm assuming the windshield was factory. On both the windshield edge and the gasket where it mates to the car, there was what can only be described as black paste. Some sort of butyl rubber that never hardened after 45 years. I had to use laquer thinner to remove it from the body.

    I do know that NAPA (the ones that sell automotive paint and supply) sell butyl windshield sealant made my Martin Senour. Here's a link to the product details:

    Hope this helps.
  8. Kustomkarma
    Joined: Mar 31, 2007
    Posts: 898


    Joined: Jun 3, 2005
    Posts: 8,043


    I want to say you need to seal at the body/pinchweld part of the gasket. The rubber does seal water from the glass side real well but the pinch area is somewhat irregular. Early Vettes will piss all over ya if you don't seal the body side. The sealant is a non-hardening product that comes in a gig that looks like an oil squirt can. We have some (we're originally a glass and trim shop) but it's 40 miles away so if I remember I'll post it tomorrow. We just did a 54 Packard W/S and used it.
  10. 62rebel
    Joined: Sep 1, 2008
    Posts: 2,744


    i've replaced Falcon/Comet and fullsize Ford windshields that used rubber gaskets and every one seemed to be different. some had a grey-white paste in the body channel side of the rubber, sometimes it was black, and a couple of times there was nothing at all. IMHO once the trim (if any) is in, and the retainers are screwed down tight, the rubber is all the seal you need. you could lay a bead of 3m window seal in the bottom of the body groove before you install the glass if you think you need it. it comes in a roll and in a couple different sizes. doesn't harden if i recall correctly.
  11. BELLM
    Joined: Nov 16, 2002
    Posts: 2,588


    Ive seen stuff that seems to be like strip caulk under windshield gaskets, still pliable when I took the old gasket & glass out after who knows how many years. I guess if you have some irregular surfaces around the lip you could get black strip caulk and spot seal that area if you do have a leak, or when installing on an irregular surface.
  12. 40StudeDude
    Joined: Sep 19, 2002
    Posts: 9,406


    Obviously you've never worked on old cars then...

    I've had the windshields replaced in three (count 'em --3) cars ('40 Stude coop, '57 Chevy hardtop and a '57 Chevy 210 two door), and each time I bought a NEW LYNN STEELE WS gasket for each...NOT ONE of them sealed, "the way it was designed"...each one of them leaked, in the corners especially...

    So before you blame it on the Lynn Steele gasket, the installer or the new windshield or the factory, perhaps you should listen to other people that have had the same problem...leaks do happen, the gasket sometimes is not enuff to prevent it.

  13. Kustomkarma
    Joined: Mar 31, 2007
    Posts: 898


    As you guys can see, there's a lot of opinions on how to do this.
  14. pasadenahotrod
    Joined: Feb 13, 2007
    Posts: 11,776

    from Texas

    Reproduction gaskets are made by a best guess method from old parts and even NOS parts...rubber is not known for retaining true mfg shape or dimensions.

    The oem gaskets were in fact designed to be used without sealant.
    This is not to say that in the field a sealant may not have been used or found necessary in some case.
  15. I pulled the windscreen out of my 38 to re seal it, thought the water was getting in around the rubber gasket. That was until I went to pull the screen out and the front of the frame came away from the rest (Its normally one part) rust had eaten away the frame but left the chrome outside looking great! I had to glue the screen in Chinner V butt style as I couldn't find a new frame for a while.
    Way O/T but if your 30s Ford is leaking, and most do check it out.
  16. fasttimes
    Joined: Sep 15, 2008
    Posts: 181

    from NC

    A 57 Chevy we just finished with Brand New Glass Rubber Moulding was leaking (the Front Windshield). My brother that used to work in the Restoration business sealed it up with 3M strip Caulk (aka Dum Dum putty) its a 1/4" thick strip that stays pretty pliable.

    The Glass was installed by a Professional, they came out again to pop it out and did a reinstall. The Glass guy also recommended the 3M product or a product called Sika (Sikeflex 220T) it is a urethane glue that does not harden up. The company that we used to buy the Moulding from was not much help. The guy just said we can not gauranty against leaks.
  17. Kustomkarma
    Joined: Mar 31, 2007
    Posts: 898


    Thanks, actual product names is what I'm after. Anyone else?
  18. BELLM
    Joined: Nov 16, 2002
    Posts: 2,588


    Working on my '55 Nomad today. Pulled out the Body by Fischer Service News # 3 1955 Model, Vol 14-11 Chevrolet Body Information Station Wagons and Sedan Delivery---installation of windshield glass--page5 "apply ribbon of medium-bodied sealer completely around base of rubber channel". This will seal around the flange/lip.
    page 6 "seal outside lip of rubber channel around perimeter of windshield, using weatherstrip cement".
    Looks like this was how GM was doing it back in 1955.
  19. Tetanus
    Joined: May 20, 2007
    Posts: 210


    Had a 55 f100 I painted whole truck and put new seal on windshield onto new cleaned-painted cab and it leaked.I didnt use any sealer,I should-would have if I knew there was some.Looked like it was leaking on the cab(metal) side because its so thin the seal cant pinch it like the glass side.Sounds like a good idea to get some of that nonhardening goop and put it in there.
  20. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,276


    I bought a tube of urethane at Advance Auto yesterday, $19
    I'm putting new vent glasses and door windows in a 1960 F100,
    Monday I will put a new back glass and gasket in my 39 ford truck
  21. Vulkem 116 - 1 part polyurethane, comes in many colors including black

    Made for houses but will seal any leak. 50 year warranty.
    I could build a boat out of it if I had enough time.

    Last edited: Jul 12, 2009
  22. jakesbackyard
    Joined: Feb 13, 2007
    Posts: 645

    from ND
    1. Upholstery

    Here's the 3M product that was used for years. I see on the 3M site it is no longer available. But check....I found it in the pint and in cartridges doing a search. A special pump with a flat plastic tip was used to pump it into the area both between the glass and gasket; and the gasket and body. The glass was usually put in and then checked for leaks. If it leaked, you figured out where and sealed it. If it didn't leak you left it alone.
  23. jamesgr81
    Joined: Feb 3, 2008
    Posts: 265


    That 3M glazing butyl caulk works great. I can almost guarantee it will leak without it. Good OEM American made gasket and body free of rust or deformations no sealer needed but after all these years gaps are bound to occur.

    Mine leaks after I listened to my buddy who told me not to use it when I wanted to. Damn it I wish I hadn't listened to him.
  24. The best sealer I've found for rubber gaskets is 3M bedding & glasing compound. Use the byutl, not the ureathane. 3M flow grade works best but they stoped makeing it. Seal between the rubber & the body & the rubber & the glass both. Its a lot less mess if you can seal them after you get the glass in.
  25. Kustomkarma
    Joined: Mar 31, 2007
    Posts: 898


    Thanks for all of the responses. I ended up ordering a couple of tubes of 3M Bedding and Glazing Compound. I'm going to apply it between the body and the gasket and the glass and the gasket. I'm going to carefully remove the windshield and start over. The screw holes for the top trim piece need to be shifted over about 1/8 inch to line up anyway. I'm pretty nervous about breaking the glass as I've never taken the windshield out of this car, only installed it. The last one was broken, so I carefully kicked the crap out of it to remove it. :D
    Joined: Jun 3, 2005
    Posts: 8,043


    CRL1716 from the C.R. Lawrence co. It's used on the body side in the base of the gasket for new, both sides for re-using the old. 61 Chev shop manual says to seal the gasket as well. Good luck.
  27. I've been doing autoglass since 1965, nothing but old cars since 1992. doesn't make me an expert but I've fixed more mistakes than most.
    everyone has favorite products and most work if used properly.
    flow grade was never intended for a sealer. it was designed as a after sealant to fill pin holes.
    I quit using 3-M products after several cars I'd used bedding compound on came back looking like cracked chalk, in less than 2 years. I like the Adco line of butyls and still use alot standard U-418 Ureathanes
    I can't think of a post 1948 U.S. car that wasn't sealed at the factory. I don't seal some strictly show cars. but anything that might get driven gets sealed and I still get one come back leaking every year or two.
    I'll start shooting some photo's of the next few cars that go thru my shop and do a tech on my way of sealing different types of sets then open up the forum to other ways that are being done and we'll all learn something
  28. Algon
    Joined: Mar 12, 2007
    Posts: 1,215


    Sika 220+ urethane cures to about the rigidity of a suspension bushing and is rated at a holding power of 1000-1200 psi. If you see the professional again ask if he's ever tried to remove a window bonded with Sika before. Its really not something you'd want on your classic car for window sealer.
  29. Can you tell me if the 65 Falcon Windshields are all the same......hardtop, sedan or ranchero ?


  30. Rich B.
    Joined: Jan 23, 2008
    Posts: 761

    Rich B.
    from Portage,IN

    Done several 50's-60's with the bedding seal. Here's a pic with
    a couple home made tools.

    Attached Files:

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