What is this part I found in my oil pan?
 

I got my engine out of my '89 190E 2.6 and found these in the oil pan. I broke a timing chain so one of the parts is half of one roller that was missing from the chain. But what is the second part?

As you see, it is quite small. One end is threaded and the other has a tapered head with a very small allen socket in it. I don't know of any part in the engine that has anything like this.

Suprisingly, it is the same size as the interior of the chain roller and about as long. I've never heard anything like it, but it almost looks like it could have been the pin that goes in the roller. I know it isn't though because the pin is intact on the other end of my broken chain.

Can anyone help?

Perhaps someone had a chain failure before you got the car.

The engine did have a top end before I bought it for an unknown reason, but it seems unlikely that it would not have come out in one of the many oil changes.

I don't think it is a threaded chain link anyway. I have never heard of one being used in a chain design. Any engineer who would have come up with that idea should be shot. What would the threaded end thread into anyway? A little nut that would shear or vibrate off?

It is a most interesting little part though.

Anyone else with a guess, or maybe know of someone I can ask?

wow my guess on that tapered threaded rod would be for a trim piece yes you heard right a interior trim piece speaker or something like that or even a headlight screw :confused:

I looked closer at the part. It is a 3mm x .5mm thread. It has a 2mm allen soket in the top and I'll guess it was about 1/2 inch ( 24-25mm) long.

It looks suspiciously like a TEMPORARY chain link pin that we used to use to "roll in" a new chain on the old Honda motorcycle OHC engines. You would press out a link pin, attach new chain to old with a similar pin to what is pictured (it was designed with the Allen recess due to some pretty close quarters in the air-cooled mc engine, if I remember), roll in the new chain, REMOVE this temporary pin, place the the new permanent pin and deform/mushroom it with the little press. We looked upon our little Allen bolt as a TOOL, not meant to be used to hold the chain together when fired up. Really have not seen anything like it since the "C" clip was used most often and ours was much smaller than the one pictured and lacked the nice taper. This was ~35 yrs. ago, so I could be wrong.

I'll ask my MB expert next time I see him if such a screw is used anywhere in the 190 -- terribly small for a engine part!

Peter