Thanks for the responses. I'm going to peel the ceiling this week and get it all protected and sound deadened before I put the new headliner in.
It's definitely dry but not brittle at all or soft and gummy. It's hard as a rock. If you look at the picture you can see all of the spots they applied the glue. Scraping it off definitely won't work. I'll try a wire brush but not I'm afraid to blister the paint. Ha does it have to get pretty hot in order to do that ? I plan on putting some adhesive spray and some sound deadner after I paint it with por15depends on what is left of the adhesive. If its dry and brittle a wire cup on a grinder will make quick work of it. Just don't overheat the panel and blister the paint on the other side. If its soft and gummy then some sort of adhesive remover, heat gun and a scraper will help you get most of it off. Doesn't need to be pretty just clean enough for something else to adhere to it and cover it up.
I used foil backed insulation for water heaters and some 3m spray adhesive on the roof of my car when I did the headliner. Its light and made a huge difference. I noticed it was nowhere near as tinny sounding especially when driving in the rain
I think I'm just going to clean it and scrape it the best I can. I don't think it will be a huge deal and it's more of a preventative thing than anything. If even if it was uncovered it probably wouldn't ever rust all the way through. It's garage kept and never driven in rain or snow. I'm just going to clean, por15 it and throw some sound deadner upI wouldn't worry about getting it spotlessly clean. You are going to cover it up anyway. If the glue is stuck that well, then I say leave it. Whatever you do, don't hurt the skin of the roof or blemish the paint on the outside. The 3m Adhesive remover is awesome stuff. It's expensive, about $25 for a quart but it works great on most glue. If you can soften up the glue, then whatever is stuck to it will soften up too. Cover your floorboard with plastic to protect it and keep it clean.
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