Author Topic: Windshield replacement - where exactly does sealant go?  (Read 465 times)

raueda1

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In the course of investigating windshield replacement I've been unable to get a clear understanding of how, when and where to use the sealant.  In the channel between the rubber gasket and the glass?  Around the body flange?  And is this before or after installation into the car?   The MB manual isn't at all clear.  And the guy that made this great video doesn't mention it all that I noticed.  https://www.youtube.com/watch?v=v4hAT0aSIyM

All advice welcome, thanks!
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Windshield replacement - where exactly does sealant go?
« Reply #1 on: 09 April 2018, 04:41 PM »
Yup the sealant debate is a tough one  :)
The manual says to put sealant between the glass and rubber seal on the outside.
Some guys put a bead of sealant into the body cavity before you introduce the window and seal. Or you can do both of course.
Either way it’s a messy endeavour so cover up as much as you can and wear gloves. 3M adhesive remover works well for cleanup.
For sealant only use “3M Glazing and bedding compound”.
3M FTW baby ;)
« Last Edit: 09 April 2018, 07:27 PM by daantjie »
Daniel
1977 450 SEL 6.9 - Astralsilber

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Re: Windshield replacement - where exactly does sealant go?
« Reply #2 on: 09 April 2018, 09:26 PM »
Yep, it’s a tough one. I used sealant on the body aperture, a bead in the right angle section. Then once fitted, I pushed sealant in the glass channel with a plastic putty knife all the way round. Afterwards, I injected sealant around the perimeter under the outer lip where it runs against the body... particularly in the corners, really pumping it in there.

There’s no leaks at present.



Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394

raueda1

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Re: Windshield replacement - where exactly does sealant go?
« Reply #3 on: 10 April 2018, 08:58 AM »
Thanks for the tips.  Here's the $60000 question:  If the sealant is NOT used, then is it a sure bet that you'll have leaking problems?  Or, if everything is done properly then leaks are unlikely and the sealant is more of an insurance policy?  I'm inclined to use it in the gasket's glass channel before installing it and then seeing if that's water-tight.  Or is that a bad idea?
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Windshield replacement - where exactly does sealant go?
« Reply #4 on: 10 April 2018, 10:35 AM »
This is kind of a "how long is a piece of string" question 8)
The design of the seal is actually pretty good, and in my opinion if you get a "perfect" installation you "should" not get any leaks.  But...
This is such a prick of a job, that I think most guys add the sealant, at least in the body cavity, as piece of mind.  If you want to be absolutely sure of no leaks, then I suppose sealant in both the cavity and the outside between glass and rubber would be prudent.
Just learn from my mistake on not using TOO much sealant on the cavity. 1/2 inch bead at the most, closer to 1/4 is probably better. When I did the rear glass it worked pretty good with a fair amount of "ooze out" but I got it to seat well.  On the front I must have used a bit more as I could not get the bloody rope to pull the seal in.  But then again the front seal is a lot harder in general so it might not have had anything to do with the amount of sealant. So what I ended up doing was sealant in the cavity only on the back, and no sealant on the cavity or glass in the front.  Time will tell if this was foolish or not.  I am waiting for warmer weather so I can hit the front seal on the outside, as I now effectively have no sealant on the front glass, which makes me a bit nervous.
So I guess i did not really answer your question, but there really is no 100% right way to do this unfortunately, do what works and hope for the best ;D
« Last Edit: 10 April 2018, 02:42 PM by daantjie »
Daniel
1977 450 SEL 6.9 - Astralsilber

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Re: Windshield replacement - where exactly does sealant go?
« Reply #5 on: 10 April 2018, 11:12 AM »
My take on this is to use as much of the proper non-hardening sealant as needed to seal all areas. If the windshield seal surface of the car body is in good condition, a new seal should seal it completely if installed correctly. However, with time the seal will harden and then leaks can start. Non-hardening sealant tends to stay a bit soft, stays bonded to both surfaces, and will continue to seal out moisture.

My opinion is to install sealant between the glass and the seal before installing it in the car. I say to also put sealant on the body before installation as well, but like daantjie mentioned, don't use too much (though I think factors like cold weather, using aftermarket seals, or having bits of the old seal or sealant still on the body have a lot more to do with this). After installation, clean off whatever squishes out and apply more if you think there are any gaps.

Also, only do this in a warm environment or it will be a total hassle.
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ptashek

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Re: Windshield replacement - where exactly does sealant go?
« Reply #6 on: 10 April 2018, 02:10 PM »
The design of the seal is actually pretty good, and in my opinion if you get a "perfect" installation you "should" not get any leaks.  But...

With current seal and windshield available from MB, without sealant between the glass and seal, it will gingerly leak through in the bottom corners.
Mine's filled all around with non-setting glass sealant and hasn't leaked a drop in two years.
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raueda1

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Re: Windshield replacement - where exactly does sealant go?
« Reply #7 on: 15 April 2018, 10:38 AM »
Great advice here, thanks to all. 

As an aside, getting an OE replacement started to look like a long project so I ended up with an aftermarket windshield.  They dropped off and it was just US$100!  cheaper than junkyard prices.  The guy was an old timer and seemed to know all about W116 pull-the-string install trick.  My OE gasket fit perfectly (if that has any significance).  Now I'm just waiting for a run of good weather.   
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

ptashek

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Re: Windshield replacement - where exactly does sealant go?
« Reply #8 on: 15 April 2018, 01:46 PM »
Great advice here, thanks to all. 

As an aside, getting an OE replacement started to look like a long project so I ended up with an aftermarket windshield.  They dropped off and it was just US$100!  cheaper than junkyard prices.  The guy was an old timer and seemed to know all about W116 pull-the-string install trick.  My OE gasket fit perfectly (if that has any significance).  Now I'm just waiting for a run of good weather.

If the aftermarket part was made by Pilkington, it's as good as OEM, just a hint thinner (0.3mm, if memory serves), which is also why it's cheaper.
The OEM part is also made by Pilkington. The original panes were marked "Securit", but that brand has been retired after Pilkington bought them.
« Last Edit: 16 April 2018, 01:28 AM by ptashek »
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)
1977 "Milan Brown" W116 350SE (parted out)

TJ 450

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Re: Windshield replacement - where exactly does sealant go?
« Reply #9 on: 15 April 2018, 07:45 PM »
Saint-Gobain Sekurit still exists, it may be the Sigla brand, they were used for front and rear screens generally, Sekurit for the side glass.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394

daantjie

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Re: Windshield replacement - where exactly does sealant go?
« Reply #10 on: 15 April 2018, 08:48 PM »
Saint-Gobain Sekurit still exists, it may be the Sigla brand, they were used for front and rear screens generally, Sekurit for the side glass.

Tim

Yes I have Sigla on mine. Data card says "heat insulating glass".
Daniel
1977 450 SEL 6.9 - Astralsilber

ptashek

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Re: Windshield replacement - where exactly does sealant go?
« Reply #11 on: 16 April 2018, 01:31 AM »
I stand corrected, got my brands mixed up between the W116 and W124. Sigla is owned by Pilkington. Sekurit is owned by Saint-Gobain. Both Sigla and Sekurit glass was used on the W124, and Sekurit was used on the W116. However, the current OEM part you get from MB is made by Pilkington (see pic below from my W116), not Saint-Gobain.

The internal part number is M1250, and DOT682 indicates it was manufactured in England.
E1 means it's safety approved for the German market (and by extension all of European Union).
AS1 means it's safety approved for the US market.

It's interesting to see mention of Sigla on the W116. I didn't know they made glass for that chassis too.
All of the OEM glass on my two cars was branded Sekurit.

« Last Edit: 16 April 2018, 01:39 AM by ptashek »
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)
1977 "Milan Brown" W116 350SE (parted out)

TJ 450

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Re: Windshield replacement - where exactly does sealant go?
« Reply #12 on: 16 April 2018, 03:49 AM »
It could vary depending on market and the different standards too.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394