4th Gen Roof bubbles & blisters – FIX????

///4th Gen Roof bubbles & blisters – FIX????
4th Gen Roof bubbles & blisters – FIX????2019-09-24T11:41:33-05:00

Home Forums GMMG Car Owners – PRIVATE Technical 4th Gen Roof bubbles & blisters – FIX????

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  • daytonajim
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    4th Gen Roof bubbles & blisters

    As the founding member of the GMMG Registry I’m looking for a fix for all GMMG Owners & am willing to use one of my cars. – (HRE #1972). – I expect that this will be an interesting topic.

    I’d like to start the discussion & ask others for their input. – Especially Jeff Foster who painted many GMMG’s. – There has been a lot of discussion & many threads on LS1 Tech. – See link below. – I’m attempting to determine if there is a solution short of replacing the roof & sail panel.

    GM made a change with the glue/adhesive at some point in time. – Does anyone know what year or is it all 4th Gens? – What did GM change from & change to what? – When the cars are in the sun there is some kind of chemical reaction & the glue weeps/leaches thru the fiberglass, primer & the paint blisters. – Most all 4th Gens have this issue but the black cars & darker color roofs really show the blisters.

    In speaking with many including Jeff Foster the correct fix is a new roof & sail panel with the CORRECT Glue. – As many already know GM discontinued the fiberglass sail & roof panels. – Many including myself are looking for another fix. – The heat & sun is the problem – glue leaches thru to primer & paint.

    Here’s an e-mail Jeff recently sent me. Very interesting…………


    This thread is very long, but here’s a link to where I chimed in while doing Vince’s car.


    My thoughts were that I had HOPED the reaction of the glue leaching through was over with age for the most part based on observations of my own car. – In other words, give it enough time and it is done bubbling. – But I don’t think that is correct anymore.- I still DO believe that if the top is subjected to enough heat for a prolonged period, you can get the reaction to slow down tremendously.- Work it out of its system sort to say. My car has been outside a couple years in the sun to get it out and that’s what I based my theory on. – And I do believe at a certain point the leaching stops. – So, my new theory is that if prolonged heat is thrown at the top for an extended period of time, you can get it to work its way out and stop at some point. What point that is will vary greatly as to the storage degree of most cars and how it has been shielded from the elements for the most part. Good for the car, but not for these tops. Hope this makes some sort of sense. –

    There are so many questions????

    Can extended heat force enough of the glue to leach out & eventually become neutral?
    How much heat & for how long?
    What is the exact glue GM used that is defective so no one uses it again?
    Why is the chemical reaction severe on the 4th Gens & not other cars?
    Do the Trans Ams have the same issue?
    Is there a different type of primer that can be used?
    Does anyone have any connections within GM that might have a solution or the answer? – This is a GM issue that they really should be taking care of but that will never happen. – Maybe GM needs to reproduce more roofs?

    I’m sure many others will have questions to ask. Please feel free to post.
    After a lot of thought & research I thought I’d mess around & experiment with HRE #1972 & try a couple of different things. – #1972 is so super nice but had a few minor blisters…. – Not bad but I could see them & I want things perfect & I am so anal about it. – My personal friend Ron has painted his entire life including being the painter @ a Chevy Dealership for many years. – He’s good!

    ROUND 1: Roof was sanded & primed (3 coats). (Photo #1)

    Ron put the car outside to blow the dust off & in the sun & heat for a while & immediately there were blisters starting to appear. – He was able to brush the blisters off & add more primer. – The blisters were exactly where the old ones were & it was very obvious the glue was leaching. (Photo #2 & #3)

    Ron & I discussed this & thought we’d re-sand, re-primer & paint the roof. (#4) – The car was kept inside for a month or so & was perfect with no indication of any paint issues. – The first time it was in the sun I could see the start of blemishes in the paint. – It’s not bad, better than it was & barely noticeable BUT I knew it was there. – I’m guessing most people wouldn’t notice it but my guess is when it’s in the sun for extended periods of time there will be more blisters.
    (Photo #4)

    If ANYONE has a solution, I’d sure like to hear about it before we start Round 2.

    ROUND 2: Coming soon… Seeing as heat is the issue with the glue, we are planning to put the car in the paint booth & put some heat to it. – The unknown is how much heat & for how long? – I’m looking for ideas from knowledgeable painters or anyone that has done this. – The thought it to try & force the glue to leach out & get to a neutral situation. – Then re-sand, re-prime & repaint. – Do you think this will work?

    Thanks ahead of time for your thoughts & ideas.

    Jim Smith – GMMG Registry

    Photo #5

    Photo #6


    • This topic was modified 3 weeks, 1 day ago by  daytonajim.
    • This topic was modified 3 weeks, 1 day ago by  daytonajim.
    • This topic was modified 3 weeks, 1 day ago by  daytonajim.
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