Brett San Diego

I have my car (78 911 SC) up on stands for a complete brake job (calipers, rotors, pads, and brake lines). I poked at the crud coating the wheel wells for a few minutes. It would come off with a light fingernail scratch revealing decent paint underneath. So I decided to clean it all off. Most of it came off with light rubbing with my fingers under a stream of water. Pics.

before


part way there


done


After a few minutes into the "cleaning," I had this feeling that I was removing factory undercoating rather than dirt. Was I? Did the wheel wells come from the factory with a black coating on them? As I reached the bottom of the fender lining, the "dirt" did get a little harder to remove so I didn't scrub too hard as I thought it was certainly undercoating at that point.

Brett

martyg

I have not read any other posts.

The section or scratch to the right of the brake does not have coating. You can tell if you removed factory undercoating becuase it is very, very difficult to get off.

Marty

Buffalo

It is many years of grime. I did the same thing several years ago and had the same concern on my 82 sc. A thorough cleaning obviously had never been done. However, I had to be careful, as even my modest electric power washer could remove the paint.

earlyapex

I also have a 78 SC and I had some pieces of the undercoating come off after the roll bar installation caused allot of heat to build up in the wheel well. I pulled off the peeling sections and there was bare metal under it. From your pictures, it looks like you removed old road grime and not the undercoating except on the last picture where there is a scratch as Marty pointed out.

Peter Zimmermann

Congratulations, Brett, you're well on your way to becoming a concours guy! The black crud was simply that, crud. Road grime built up over the years. No, you haven't hurt anything, enjoy...
Pete

911Dave

In the process it appears your rotor picked up some surface rust. Better go drive it off!

Alan Herod

The factory sprayed the undercarriage with that textured, relatively soft, body colored stuff called 'Body Schutz'. Over every thing underneath they may have sprayed a thin layer of cosmoline which is a light tan color. The US dealer net work put that black undercoating over body colored surfaces underneath. My guess is that they thought the US customers expected it.

M491

Very nice! You did that with just water, no cleaners?!?

Brett San Diego

The bulk of the black stuff came off with a light rubbing. I finished it with a medium sized plastic bristled brush (toothbrush for tighter spaces) and some Simple Green degreaser.

Brett

Dan Cobb

That scratch appears to be from a rubbing tire (past or present). I would check that out and if nothing mechanical is required, at least get some type of coating/sealer over what looks like bare metal or primer.
I'm not sure which would be worse, bare or primed because I do not know if the factory primer is water-proof or not. Most used on US cars is not.
+++

Brett San Diego

Yes, it does look like a tire rub. I'll get it to a body shop when my brake job is done.

SRL

Aren't you glad it wasn't blue under all that???

Brett San Diego

hahaha. Very!