These are pictures of my C36 AMG M104 engine with the heads removed.

Please take a look at the color and slight build-up on the top of the pistons.

Is this normal? The sides are smooth with no nicks or burrs.

Should the piston tops be lightly finished?

Does the color and pattern indicate anything?

What else should be checked or done while doing a valve-job and head-gasket?

Thanks in advance,

:-) neil
1988 360TE AMG
1993 500E

That is carbon build up right? I had bad luck with platinum plugs not running right. You know it is possible that the oil was leaking down near the spark plug holes and making a burnt on coating on the pistons.

That maroon color doesn't look quite right. Ill show the pictures to some people and get some more opinions for you.

I would say getting that stuff off would be a good idea at the least.

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

The "maroon" colored stuff is a light coat of anti-corrosion oil/ATF while the head is off.

:-) neil
1988 360TE AMG
1993 500E

IMHO I wouldn't worry too much about the piston tops. Remove what you can remove relatively easily and don't worry about it - You can use a Dremel with a wire wheel, but that tends to throw bits of crap everywhere.

More important is the condition of the cylinder walls. Can you see any honing marks? The honing in the cylinder walls is what keeps the oil film in place and lubes the pistons and rings. If your cylinders are "polished" i.e very shiny with no honing marks, your oil consumption will increase and you will develop blowby from worn rings, etc. Small streaks of polishing are somewhat normal and don't matter too awful much.

Unfortunately you can't do anything about the cylinders without doing MAJOR work to disassemble your engine further. But you probably know all this above anyway!

Don't know why you have pulled the engine down this far, presumably to repair the head. Hats off to you anyway for tackling this job - it's much more than most DIY'ers would be willing to do on a modern car with packed engine compartment like most MB's these days!

Rgds,
Chris W.

Neil -

Just a little bit of carbon - you need to stop grannying this car and drive it harder!

- JimY

When my 95 C36 had a head gasket a couple years ago with about 55K on the odo (benzmac did the work...) it had some carbon buildup on the pistons. It would seem to be pretty normal. Mine never used any oil whatsoever...

Hope this helps,
Lee

Unfortunately you can't properly clean the tops of the pistons without removing the piston. Anything you remove is likely to get lodged between the pistons and the rings or walls.

The build up looks excessive. It probably is unburnt fuel than anything else. When I torn down the E320 block with 68K for my 190 it didn't have any build up. Just carbon discoloration that wiped off with Marvel Mystery oil.

If you are very careful you may use a HD wet dry vac and a cloth to try and remove any loose debris. Place the vaccum in the bore that you are working on. Remember what what the dentist does with suction so those teeth chips don't go down your throat while he is drilling!

Also reccomned you BP/Ammoco Premium "CLEAR" gas. Most of the street rod guys around here run it on their street machines and swear by it.

Sometimes fuel "Additives" and "Cleaners" in some premium fuels are the worst for the car. Remember marketing never did any good engineering work.