Door skin glue/foam showing in metal

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PostPosted: Fri Jan 27, 2017 7:01 pm
I am restoring a 1987 vw syncro westfalia and I have struggled on every sliding door I have every done on one of these vans. My process started with a that was a vehicle dustless blasted to bare metal. I then epoxied all panels. This particular door was followed up with a couple skim coats rage extreme filler. The filler was roughed out with 36, then skimmed again and finished 80/120, then a final skim blocked and guide coated with 120/180 until I can't feel any dents and there is no guide coat left on the panel. I then filler prime the panel and block with 80/180 and then wet check again and little dents can be seen all over where the factory glue/foam is attaching the panel to the skin, where the glue is sandwiched between the brace and the skin and the skin from behind the panel. I am not using any heat on the panel other then shop temp of 70 degrees. I slide the block when blocking barely any pressure and even strokes. I have tried making one of these door straight many times but always end up with a door that shows these marks/dents where the factory glue is beneath.

Someone has to have dealt with this before and have a good solution??? My initial thought is to cut the glue to release the panel and see what happens. Then if needed add filler or block the panel again and see if the marks go away when there is no glue holding the panel back. The issue then would be adding the glue/foam back in later and not seeing the marks from the new glue I inject in there. Thanks for any of your help and saving my sanity.

Casey

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PostPosted: Sat Jan 28, 2017 10:40 pm
syncrodriver wrote:.........thought is to cut the glue to release the panel and see what happens. Then if needed add filler or block the panel again and see if the marks go away when there is no glue holding the panel back. The issue then would be adding the glue/foam back in later and not seeing the marks from the new glue I inject in there. Thanks for any of your help and saving my sanity.

Casey

That's a good plan except I'd use panel adhesive and bond the panel to the brace
before filling and blocking again. Try to remove all of the old glue that's possible,
then bond the brace/panel using 3 inch strips of adhesive leaving 3 inches open
between bonds. (Sort of a stiching pattern if that makes any sense.) Then do the
filling/blocking. That should do the trick.
"If you can't move it, paint it." - U.S. Army



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PostPosted: Mon Jan 30, 2017 8:57 am
Thanks NightTrain! I am curious why its happening. I mean the panel blocks flat? I just see it when I wet check it which means the lows are in fact there just not able to feel by hand or see with guide coat. The factory glue on the brace is pretty hard like panel bond. Would 3m flexible foam be better for this application. Just curious since its pliable where panel bond is hard.Thanks

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PostPosted: Mon Jan 30, 2017 11:16 pm
syncrodriver wrote:Thanks NightTrain! I am curious why its happening. I mean the panel blocks flat? I just see it when I wet check it which means the lows are in fact there just not able to feel by hand or see with guide coat. The factory glue on the brace is pretty hard like panel bond. Would 3m flexible foam be better for this application. Just curious since its pliable where panel bond is hard.Thanks

I suspect the problem is caused either from temperature variations or stress on the
door panel when opened or closed for the first time. The metal is probably thin and
who knows what kind of glue VW used on the bracing...?

The 3M FlexFoam is an expandable foam, and I don't know if it would work or not.
I haven't used it. Another option might be a urethane seam sealer that stays flexible.

The 3M foam is advertised for door, trunk, hood, top bracing, etc,, so it might be
worth a try. Maybe someone will chime in that's used it...
"If you can't move it, paint it." - U.S. Army

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PostPosted: Mon Feb 13, 2017 11:14 pm
OK, I saw this exact problem on one of the TV car shows today.
It was on a hood that showed uneven areas after being painted black.
The cause was panel flex when block sanding. The area above the
glued bracing was supported more than the rest of the panel, and
allowed the slight flexing that resulted in the shallow dents (when blocking).

In your first post, you seem to have done everything correctly. The only thing
I might add is to spray more filler primer on the bonded areas, and use a
sponge to lightly do a final blocking. A soft touch seems to be the key,
especially on a large thin metal panel like your VW door...
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PostPosted: Tue Feb 14, 2017 12:33 am
Hey, NightTrain, was that the black El Camino on Gas Monkey? When I saw that I immediately thought about this thread......man this world just keeps getting smaller.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Tue Feb 14, 2017 8:00 am
I just keep reading and learning.



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PostPosted: Tue Feb 14, 2017 8:21 am
Thanks guys. Just watched that episode too. I have tried it all, at least feels that way. Soft block, hard block and light touch. It's definately the panel forcing from the weight of my arms. I even hung the door and tried blocking that way to take the weight of my hands and arms off the door. No luck. Blocks all guide coat off and the shallow dents are still there. Had a very respected pdr guy come and he said im ocd that it may thought to get it better then it is already. One suggestion he had was to put some sound dead wrong between the brace and the skin to push out to where it looks right. He said the memory of the metal is the problem. The metal blocks flat but slowly pulls back where it was for the past 30 years. I'm still not satisfied. I'm going to try and block with a hard block again to level it, reprime high build and give it one last caress.



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PostPosted: Tue Feb 14, 2017 11:39 am
One thing I've learned is that the panel should be sanded in the normally closed and latched position. This is especially true on hoods. Blocking either on a stand, or with the panel open places a different stress on the panel subframe than when it's closed and latched. When you close it, or take it off the stand, the subframe will usually pull from the underside (latch area and then transfer through the subframe) as well as, at least on a hood, push up on the corner bumpers causing a depression.

Short of that, a modest skim coat of filler over the entire length and width may help.



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PostPosted: Tue Feb 14, 2017 9:14 pm
Funny you should mention that Kevin. I have been blocking the door laying on a stand. Today I noticed that the doors subframe is resting right on the stand which could be pushing the subframe and making the high spots on the outer skin. I now have the door hanging on one of my paint stands like it is oriented on the van. I gave the panel a nice swipe of topcoat and will try and knock it flat tommorow with a good hard block first with 80 to get my shape then with 180 while keeping no pressure on the skin to keep it from flexing. If this doesn't work I'm moving on.
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