535--Noticed carbon in one of the exhaust downpipes

[mikemaster]

While I was changing out the guibo (which I have to post some pictures of, it was shredded!) I noticed alot more carbon buildup in the front downpipe, from the front 3 cylinders on the engine. Does this indicate anything in particular? I don't use any coolant at all and not much oil, maybe half a quart in 3,000-4,000 miles. Just curious as to whether anyone else has seen this?

[winfred]

usually due to a slight exhaust leak blowing out a little condensation/carbon

[bill g]

I am in the process of re-installing the head and exhaust etc. on my 535i M30 after a head gasket job. Colour of deposits in exhaust manifold for front 3 cylinders is black, rear three is whitish. Maybe it is normal for these engines (my car was running OK), although the disparity in colour would suggest uneven mixture burning. I did find the front exhaust manifold gasket a bit burnt which could have been a very slight exhaust leak, although I never heard any leak.

Bill G