I ran into a strange situation yesterday while doing a valve adjustment on my
'83 240D. Halfway through the procedure, which I have done many times, I
noticed a very audible "springy" squeak when I manually turn the engine as in
rotating a cam lobe to the right position. It first occurred after I had left
it for a while about halfway through the job and had come back to it later.
I'm sure I did not hear it until then and I believe it is loud enough such
that I would have heard it the last time the engine was running the day before I removed the valve cover to start the job.

A check of timing chain stretch at the start of the routine showed ~4
degrees. I'm not aware of anything falling into the timing chain recess, no
nuts, washers, or other parts are missing, and as far as I can see into the
recess with a bright light I can see no foreign items. I thought perhaps it
was coming from one of the peripheral items in the belt system, e.g.
alternator, etc. but the sound appears to be emanating from the chain recess
or the cam area. It is consistent with each rotational movement of the engine crank/chain.

I thought perhaps it was due to lack of oil on some surfaces due to drain
down, but that should be somewhat typical as any shut down period. At this
point, I'm a bit reluctant to button it up and fire it up. Has anyone had a
similar experience or any suggestions? One thought is that it could be vacuum pump noise, but it certainly seems strange that it would first occur halfway through a valve adjustment.

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Okiebenz