I blew the head gasket and have removed the head which is currently being rebuilt. I want to remove the carbon build up on the pistons. I have cylinder 1 at TDC and #6 is at the top too. I want to clean up the others, but I need to know if it is OK to turn the engine so the other pistons get to the top so I can clean. My worry is that with the timing chain loose if I turn the engine will it cause a major problem?

The timing chain must be held taught upward whilst the engine is rotated. Are you understanding how the chain tensioner works on these. I'd leak test the valves on my own after the machine work before installing the head unless the machine shop will vacuum test them while you are there.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thank you Sugar Bear for the response. I must admit I don't fully understand the way the tensioner works. I am handy and have rebuilt an engine before, but that was many years ago and not a Mercedes. I do have a manual and do a lot of research on the computer too. I have been very successful in removing the head. As always, I am trying to do the best job and be thorough. I do have the chain suspended. I also have cleaned the tops to 1 & 6 to some degree but will do some more to bet them cleaner.
Any advice and guidance will be appreciated.

I can't upload pics for some reason. I have in the past, but...???

The tensioner is a one way ratchet that will only move in the direction that tightens the chain. When the head was removed it went to the full tight position, leaving it this way will tear up the chain and gears.

The large nut on the tensioner must be removed, it is under quite a bit of spring tension be careful, then the plunger removed toward the chain. Upon reassembly after the head is installed the plunger gets put in from the outside, the spring and nut then get reinstalled.

Sent you an email last week, did you receive it?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

The chain has to be suspended and be able to roll. If it drops down it may get jammed and break a tensioner and then the front cover has to be removed.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I removed the tensioner fully. Suspended the chain. I do see where you advised that the chain must be taught. Again, trying to understand. When I rotate the engine will the chain rotate also?

The tensioner must be disassembled, the plunger removed and reassembled, removing the whole body isn't going to work.

Yes the timing chain will rotate when the engine is turned, that is good as it shows the chain is engaged with the lower crank gear teeth. If the chain doesn't rotate with the engine it isn't taught on the gear and will jam in the front cover.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Sugar Bear, appreciate the help. I will be working on this today as well as the weeks ahead since the head is getting rebuilt by an outside source. I might have more questions along the way. Again, many thanks.

I reread my post about the tensioner, on reassembly the head must be installed PLUS the camshaft, timing chain and camshaft gear before the plunger, spring and cap are installed into the tensioner.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Got it! Probably doing that Christmas week. In the meantime, prep, prep, prep!