Attached are photos of my Harmonic Balancer w/ pulley and the crank's nose or whatever you call it. Nose seems reasonable LOL.
I say LOL but this is no laughing matter. See, I recently posted a thread about losing p/s and alternator feedback all with an belt in good condition.

That thread here:all dash lights turn on when driving - loss of power streering W126

After finally getting down to removing the Water-Pump pulley in regards to replacing the Belt-Tensioner, I learned the pulley on the crank was loose enough to fall off....and it did. The metallic clanking noise sounded like death to me but maybe it can be fixed? See, the bolt is Long gone as is the small key for the harmonic balancer; which is still attached to the pulley. Before the harmonic balance articulation broke, I had a nasty knocking noise that I now know was directly correlated, but what exactly was the noise I was hearing?
Should I part out the car or attempt a machine-shop level fabrication? Does vibration Really cause a bolt torqued to 250 ftlbs to fall out on the highway?

Attached Thumbnails

     

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-“Never trust a mechanic who drives new cars. They're either charging too much money for their work, or they can't keep an old car running - maybe both.”

There's still hope.

Just to be clear, is it only the crankshaft pulley that is bad?
If so it's cheap.

However if the harmonic balancer is shot too, it will cost $860 to replace.
You are best off taking one hell of a drive to a junkyard that has a car with an om603 in it and picking the parts off the car yourself.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

I havent gotten enough of an eye on the other end to see for damages, but from the 2 photos I was able to manage, it looks like there is minimal damage.
Is there a good thread or even diagram that better explain the tooth/pin alongside the crank bolt?

__________________
-“Never trust a mechanic who drives new cars. They're either charging too much money for their work, or they can't keep an old car running - maybe both.”

Something similar happened to me. My mechanic made a blog post about it
http://artisanexcite.blogspot.com/2017/03/om603-loose-crank-bolt-damage.html?m=1
I have had both 603s in my life get loose bolts. No idea why either. First one was caught early and properly tightened before anything happened. Perhaps he can chime in if he is on here.

Interestingly enough I just read that article. I am intrigued to make this work.

Am I limited to diesel for the balance assembly, or can I consider petrol by any chance?
Have that MB part # handy??

__________________
-“Never trust a mechanic who drives new cars. They're either charging too much money for their work, or they can't keep an old car running - maybe both.”

Unfortunately I do not have the # handy, nor do I know if a petrol balancer would work, but I would assume no. I am surprised your car still worked with no bolt at all.. Mine was loose but never fell out.

Between the w/p pulley, belt, and the excess of oil residue there wasn't much place for it to go. On the flipside, I read about an instant where a pulley flew off on the hwy from losing the bolt.

__________________
-“Never trust a mechanic who drives new cars. They're either charging too much money for their work, or they can't keep an old car running - maybe both.”

The pulley on my 84 617 SD came off when the vibration damper separated a bit. I guess the movement of the damper spun the bolt or something. Evidently the oil and fuel which saturated the rubber in the damper and caused it to fail. Fortunately I was sitting in a parking lot at idle when the alt light on the dash came on.

Had it happened going down the road I'm sure I would have been much more radical.

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84 300SD
85 380SE
83 528e
95 318ic