Hi,
Removing this stuff is a pig, I have aready done one car (BMW2002Tii) and in the process of doing another (BMW 3.0Csi)
Various methods used so here is my list/ what I did.
First steam clean/pressure wash the underside as much as possible to get the loose dirt, oil and several years of road muck off the underside.
I have used an old wood working chisel and a lot of scraping, takes for ever....
Heat gun and same chisel I would not recommend LPG as you can set the stuff on fire [:0]. It can give off very nasty fumes especially if its the PVC type if stuff. Good for getting the stuff out of corners etc...
The best method I have found is to use needle gun (air driven) with blunt and rounded needles. Have it set on a lowish pressure and the needles will "chew up" the underseal and then you just pull it off.
Trouble with a wire brush is that is can smear the stuff about as it tends to melt, especially if you use an electric drill or angle grinder.
I am not sure about the colour. If the stuff was applied before the top coats then it may of been painted, or suffered from over spray, cleaning it first may give you a clue.
If you can turn the shell upside down to really get it clean, but weld/bolt a brace across the door apertures to stop the car folding up/breaking in half. (I made some door aperture braces to do this, and to turn the car through 360 degrees, like a barbie spit!)
What I then did.....
remove the rust by grit blasting (if poss, very messy) and weld in the required repair panels (if applicable
) Apply 2 good coats of zinc rich primer followed by industrial (truck/lorry) chassis paint, then two coats of body Shutz
Finally and it's a mistake lots of restorers make, they don't rustproof a newly restored car....
You need to rust proof the bejeezuz out of the car once you have the shell restored and painted but
before you start putting it back together, so you can get in all those nooks and crannies
I would recommend Dinitrol for box sections and areas not exposed to the elements such as doors etc, and Waxoyl which is heavier in the wheel arches under the floor.
So far my 2002Tii is surviving ok despite being driven in all weathers and used by my good lady as her daily hack to work!
15K miles per year I will reapply Waxoyl this year as it's been two years since I did it.
HTH
Malc
PS Even if you are in a "nice" climate, damp humid conditions or living by the sea will cause rot so still rust proof your pride and joy!
