C3 hardtop glass install
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Cruising
Joined: Jul 2018
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C3 hardtop glass install
Returning member; I'm trying to reinstall the back glass in my 68 hardtop. I may have used the wrong sealant because I can't get my trim to seat properly, it wants to pop back out. I have replaced all clips with new ones. What sealant and how thick is it supposed to be applied?
Thread Starter
Cruising
Joined: Jul 2018
Posts: 11
Likes: 0
I may not have stated my issue correctly. I'm trying to reinstall the molding and it doesn't seat. I'd like to know the correct thickness of sealant to use for installing the glass because I may have used too thick of a sealer.
Race Director
Joined: Apr 2009
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From: Charlotte NC
When I install the back glass in a hardtop. I use the butyl tape and correct primer for it.
If you used urethane....hopefully you used the correct primers and such....and IF it oozed out...you will have to cut it out......which is why I do not use urethane for this specific application.
NOW...you can use urethane if you choose..and on some hardtops that is what the owner wants...and what this causes me to do is to get the back glass in and then immediately install the trim.
The reason i prefer to use the butyl tape is much like how GM uses butyl tape for the 1973-1977 back glass in the Corvettes. The back glass is NOT urethaned in like the front windshield is. This back glass is not needing to be bonded in as a part of structure.
DUB
If you used urethane....hopefully you used the correct primers and such....and IF it oozed out...you will have to cut it out......which is why I do not use urethane for this specific application.
NOW...you can use urethane if you choose..and on some hardtops that is what the owner wants...and what this causes me to do is to get the back glass in and then immediately install the trim.
The reason i prefer to use the butyl tape is much like how GM uses butyl tape for the 1973-1977 back glass in the Corvettes. The back glass is NOT urethaned in like the front windshield is. This back glass is not needing to be bonded in as a part of structure.
DUB
Race Director
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From: Charlotte NC
I believe I have used the 3/8" thick stuff and really pressed on the glass to get it to compress. Keep in mind I am also doing this when the butyl tape is warmed up and not cold....which can make it compress a bit easier if it is warmed up well.
I honestly do not think I used 5/16" thick butly tape due to I know I can get the glass set and press on it to make it compress and get the moldings to fit.
I am assuming you applied the butyl tape correctly....and you did use the correct butyl primer.
DUB
I honestly do not think I used 5/16" thick butly tape due to I know I can get the glass set and press on it to make it compress and get the moldings to fit.
I am assuming you applied the butyl tape correctly....and you did use the correct butyl primer.
DUB
Last edited by DUB; Mar 6, 2019 at 06:08 PM.
Thread Starter
Cruising
Joined: Jul 2018
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Thanks for the input Dub!
I used the 3/8 tape in a heated garage, new clips too. But when I set the molding, it will seat on one end and the other end would pop out like the clips don't hold like they should. I have it all back out and cleaned up for a 3rd attempt. That molding should just pop back in right? Could be I'm not compressing the tape correctly?
Did you put the bedding/glazing in after the glass is set? Mine had it I'm assuming from an original install. Just to fill and seal the gap between the glass and top.
I used the 3/8 tape in a heated garage, new clips too. But when I set the molding, it will seat on one end and the other end would pop out like the clips don't hold like they should. I have it all back out and cleaned up for a 3rd attempt. That molding should just pop back in right? Could be I'm not compressing the tape correctly?
Did you put the bedding/glazing in after the glass is set? Mine had it I'm assuming from an original install. Just to fill and seal the gap between the glass and top.
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Race Director
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From: Charlotte NC
Why don't you test fit your moldings BEFORE you try to do this again.
You can use the 3M bedding/glazing compound if you want. I have stopped using the 3M stuff and have switched over to CRL 7708 which is a lot better. I have had issues with the 3M stuff and in time...water leaks would show back up.
Being in a heated garage is one thing.,..but heating up the butyl tape and seeing that if you do heat it up with heat gun...AFTER you have applied it to the top itself.... will allow it to compress easier.
DUB
You can use the 3M bedding/glazing compound if you want. I have stopped using the 3M stuff and have switched over to CRL 7708 which is a lot better. I have had issues with the 3M stuff and in time...water leaks would show back up.
Being in a heated garage is one thing.,..but heating up the butyl tape and seeing that if you do heat it up with heat gun...AFTER you have applied it to the top itself.... will allow it to compress easier.
DUB
Race Director
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From: Charlotte NC
YES...the CRL 7708 can get REALLY MESSY if it begins to come out when molding are being installed. But I much rather have some ooze otu and have to do some clean up then not put enough in and have to do it all over again.
DUB
DUB
Thread Starter
Cruising
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Clips are pretty much the same as original. I'm thinking maybe the screwhead is a little tall and when the molding goes in the head of the screw may push it out and spread the clip. It's all back apart now. still unsure how to get it all back in correctly.
Race Director
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From: Charlotte NC
I can say that the screws for the clips are a unique very shallow pan head.
If you cannot get the trim to go on .... with no glass in place so you can see what is going on....it is possible that the incorrect screws can cause this.
DUB
If you cannot get the trim to go on .... with no glass in place so you can see what is going on....it is possible that the incorrect screws can cause this.
DUB
Drifting
Joined: Nov 2002
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From: Blue Bell PA
2018 C3 of Year Finalist
The advice I gave above came from a vendor at Carlisle that only does
hardtop,I forget their name now but the guy knew just what I was talking
about . The molding didn’t want to stay tight against the glass.
the screws don’t seem to squeeze the clips closed. The homemade shims
did work. Not perfect but dam close. Not sure what the sealant has to do with it .
a glass person set mine and the sealant is not in the way of the clips.
You can get them right back off with that bent pic. The vendor told me
that to.
hardtop,I forget their name now but the guy knew just what I was talking
about . The molding didn’t want to stay tight against the glass.
the screws don’t seem to squeeze the clips closed. The homemade shims
did work. Not perfect but dam close. Not sure what the sealant has to do with it .
a glass person set mine and the sealant is not in the way of the clips.
You can get them right back off with that bent pic. The vendor told me
that to.