My DeLorean had spots on the door panels, on the windshield's post and the dash board.
It is most likely from the factory. It is from dripped adhesive glue or sloppy handling during the gluing process. The stains are the adhesive glue that have aged and turned brown. It can be very removed if you have the patience, a good hand and understanding the working characteristics of the acetone solvent. Do not work on a humid or cold day. White streaks may appear.
Wear glove to protect your hands and do this in a well ventilated area, unless you what to get "high." Work in the shade with no sun shinning on the area. The sun's heat will cause the acetone to dry too quickly and making it difficult to control.
The old glue is dried out and hard. If the stain a glue spot is thick, you will need patience and a good hand. If the stain is thin, just go to the next step below, using the acetone. The first step is to thin out the glue spot with a razor or an Exacto knife by scraping it slowly with care. Do not press the cutting edge in the surface. Just scrap the brown glue spots. The old glue will flake off. When you see and feel that the glue is thinned out and smaller in size -- STOP.
The next step requires a some care. Take a very clean rag (white) or Q-tip and dampen with the acetone solvent. Make sure it is NOT DRIPPING WET -- JUST DAMP enough to work with. Dap and wipe the brown spot area only! The acetone will "MELT" the surface of the finish too -- take care. You must get the feel of this process. With patience and some care, you will get the results. Don't rush. Work with the acetone not against it. Do this by quickly wiping the area of the glue spots only and no other area! You must rotate the rag or Q-tips between every two to three or four quick wipes -- Then stop and let dry! Also, do not reintroduce the melted old glue onto nearby surrounding area which will be soften by the acetone. The wiping of the acetone will melt the glue and the surface underneath the glue too. Don't fret. It will dry and harden up again.
YOU MUST LET THE AREA THE ACETONE CONTACT TO DRY BETWEEN EACH TIME. Repeat the process until the brown spots are remove!
Afterwards, you can give it a final swipe in ONE DIRECTION ONLY. Do the whole entire running length of the surface with a damp rag to blend in the spot with the rest of the panel or the area. This surface will feel "soften," it will dry and harden up again.
You can also clean all the other surface if you take great care with the acetone. I have clean and blended my WHOLE GRAY interior of my DeLorean. It gives it a new surface looked by cutting off the old dirty grimy surface where other cleaners can't. Then finish with a good interior car finish.
I have also used acetone to clean the surface and to fill the minor crack hair line cracks by "controlling the melting" of the gray dye. I have filled the minor cracks with the melted dye in the leather sections. Again, with one good final finish wipe with a damped acetone rag, the leather surface will look cleaner, much better then before. Do this with caution in not wiping too much other wise you may see the "tan" leather surface -- Do it just once or twice, enough to clean off the grimy layer.
Before you begin, get some experience first. Remove a panel and try this process on the underside of the panel or an area that is not noticeable. Once you are confident with the process, then got for it.
Once again. You must exercise care and experience helps.
#5508 Lic 9D NY
I passed on the procedure for removing these stains from Dave Howarth, and the chap who got the information said it worked beautifully. Work on the stains carefully with some lighter-fuel (petrol - the stuff you put in Zippo lighters) and then buff the area up with some grey (or black) shoe polish.