Thread: What is this stuff?

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When I removed my Malibu's headliner, I noticed that there is this material that was glued to the inner metal roof skin. It looks kind of like roofing felt, or a heavy tar-paper. It was peeling away in several areas, and I could see the rust underneath it,. I cut and scrapped it all off, so I could clean up the rust and repaint. Now I am ready to put the headliner back in, but am wondering what I should do about replacing this tar paper stuff.
Originally, this material was actually run between the roof skin and the center support rib, and also ran under the front. rear and side roof frames.
I could just adhere some roofing felt to the skin, right up to the edge's of the rib, and frames, but don't see how it would be possible to tuck it under the framing. Not sure if that would be an issue or not?

I am not really sure what this stuff was even used for, but I suspect it may have acted as an insulation perhaps? I know that since I removed the headliner, during certain weather conditions, (cold nights sunny days), I get lots of water condensing, on the inside roof skin.

Another idea I had was to spray the roof skin with a thin layer of expanding foam. It would have to be very thin so I can make sure the styrene headliner base, will fit properly. I felt that would act as an insulator.

Anybody have any idea, exactly what GM put this stuff on the roof for, and what might be the best plan of attack to replace it?

Thanks!

I'd replace it with Hush Mat or the like. Helps quiet the interior and reflect the heat out. My 2 cent!

How thick is hush matt?
Anything much more than hmm..say maybe 3/16", possibly less, and I may have difficulty getting the head liner in place properly.

Surprised no one knows what it was for originally? Sound damper, heat or cold insulator, anti-condensation barrier..

Surely I'm not the only one to strip a GM car down this far?

Originally it was for sound deadening and heat transfer, also to kill and rattles or other funny noises that the roof can make. You did the right thing in scraping it all off, might want to consider putting some seam sealer or something like it wherever the braces can come in contact with the roof. Last roof I did on the inside I coated the inside of the skin and crossmembers with some of the Lizard Skin heat deflector. It was a dark colored car and anything that will help kill some of the heat is a good idea!!!!

Yeah, I think Dave's suggestion of Lizard Skin is probably about the best, especially if you only have 3/16" or so. You for sure want to use something made for use in automotive interior applications and not some spray on coating from the hardware store that will off-gas every time it gets hot. That could get nasty fast.

Wouldn't condensation still form on the underside of the lizard skin, similar to the bare metal? I thought I would need some sort of insulation. IE; dead air space?

I'm still not 100% sure why this condensation happens as it does.
I initially thought that there must be a leak in the interior, to have this moisture in the first place, but I also get this same condensation happening under my un-insulated hood, and my trunk lid. I figure it's got to be something about our moist coastal air. (I live on an Island). Only happens during the colder months, when the sun shines during the day, and the outside temp's climb rapidly...

Depending on how well you are looking to insulate your Car from Heat and Noise, I think I would consider a combination of products, such as Lizardskin, Fatmat/Dynamat for the Insulative properties, and then anti-flutter Foam for the Bows (to stop noise and vibration)-

Here is one Anti-Flutter Foam (although you will need an Application gun), although there are many different Compaines offering them-I personally like Lord Fusor the best, but....

"3M™ Automix™ Flexible Foam is a soft and flexible two-part urethane material which foams in place (closed-cell foam). It is designed to replace OEM's flexible foams found on door intrusion beams, roof bows, inside body panels, and in other automotive body cavities. This flexible foam expands to 10 times its original size. Foam time takes 40 seconds, work time is 5 minutes, cure time is 1 hour."

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Here is the Lord Fusor product-

Ketone.com: Lord Fusor® 10.1 oz. Super Flexible Anti-Flutter Foam, Fast Set Formula, Foams & Sealant Products, LF121