Quite possibly the saddest question...

[rsk289]

...I've ever asked on a motoring forum.
Got the rear exhaust off at the moment as I'm doing ARB links and bushes. The exhaust needs a bit of cosmetic attention - has anyone cleaned the black (grey?) paint off and left the system in bare metal? Are there any downsides to doing this - I'm wondering if the welds are mild steel as they look a bit rusty in places, but the paint is getting a bit flaky here and there. I don't think I'm prepared to go as far as actually polishing the system, but any thoughts/experiences?

Roger

[dollag]

...I've ever asked on a motoring forum.
Got the rear exhaust off at the moment as I'm doing ARB links and bushes. The exhaust needs a bit of cosmetic attention - has anyone cleaned the black (grey?) paint off and left the system in bare metal? Are there any downsides to doing this - I'm wondering if the welds are mild steel as they look a bit rusty in places, but the paint is getting a bit flaky here and there. I don't think I'm prepared to go as far as actually polishing the system, but any thoughts/experiences?

Roger

i think its a great question

i noticed that the black on my back boxes are also flaking and was just going to respray them; however your idea sounds interesting. unfortunately, i do not possess the knowledge to answer your question. i do believe that it is not mils still though. I recently ripped my back boxes open and removed the internals. if memory serves me right. they are not mild steel

[Seca Blue]

Ha - don't worry about that, I've asked some crackers in my time.

The back face of my ACS pipes had a black coating on that was looking a bit tired. I polished the lot off and IMO it looks loads better. I know this isn't exactly what you're asking but it's all I can offer ;-)

[rsk289]

No, the boxes and pipes ahead of them are all stainless. Some of the bracket welds look rusty, so I wondered if they welded the brackets with mild steel wire. You can use either, stainless or mild steel wire to weld stainless - I've done both in the past.
Why did BMW paint the boxes and pipes, I wonder?

[kwoffa]

I think the whole back box is stainless,you might find that the rusty looking bits is just general crud,i have seen some OEM boxes polished and some re-painted,both look good to me.

[Dave P]

I have seen a set that have been powder coated black recently which looked good but maybe better in the original grey?

[fok]

Why did BMW paint the boxes and pipes, I wonder?

I asked Remus the same question and the answer was to show off the polished stainless tail pipes more.

I've seen some OEM silencers stripped and polished and they looked nice.......Quite like Supersprint.

I guess Nitromors and elbow grease or bead blasting would do it.

[rsk289]

Well, after a day with thinners, Nitromors and polish, I think it's back to paint.
The boxes upper and lower surfaces are covered in small pitted rust bubbles. These are the original BMW boxes with the logo and the part number on them, made in May '01. I guess it's down to a lesser quality of stainless (prob 304, not 316?), but I've had to use fairly abrasive paper to reduce these (can't get rid of some of them completely) and actually getting to any kind of polish may compromise the skins!
Not too concerned as my aim with this car has always been to keep it as original as possible, so painting them is OK. I think the original finish might have been satin black that has faded with time rather than grey - but if it is grey, anybody got any ideas as to shade?

Roger

[Dave P]

There's a set for sale on ebay Germany at the moment which look very original,




Colour does appear to be a dark grey

http://www.ebay.de/itm/BMW-Z3-M-Orig...item4aeadc335e

[rsk289]

Hm.. so hard to tell, in the main pic on that listing they look black.

[Spooks]

Hm.. so hard to tell, in the main pic on that listing they look black.

The paint on my back boxes is also starting to flake off now and have to wondered about polishing them up. Take them off and give them to a professional polisher, they'll come back looking great and won't cost much at all

For what it's worth, I think the paint is black

[ragerover]

Think they are stainless
Nemesis polished his iirc
Looked cool

[Fat Tony]

Nothing to add other than to say how disappointed I am with the actual amount of 'sad' of the question. Try harder next time please ;)

[rsk289]

Nothing to add other than to say how disappointed I am with the actual amount of 'sad' of the question. Try harder next time please ;)

Well, if my wife knew I was posting questions about polishing exhaust pipes....

[rsk289]

I've inspected the boxes closely and there are definite areas of rust in the surface of the stainless steel. Cleaning these with a fine scraper shows definite pitting, and given the very thin nature of stainless silencer skins I don't think it would take too much to perforate the metal. This pitting is either down to the grade of stainless, or small inclusions in the stainless which have rusted. Either way, I don't think polishing would be a good idea, so will be stripping off the flaking paint remains with solvent before keying, using a decent etch primer then finishing with satin black.