I have this part that is dripping oil. I would replace it but I have no idea what it is. The part in question is the black wire that is plugged into the copper colored part of the engine. I have traced the wire back and it looks like it is plugged into the glow-plug relay.

Attached Thumbnails

     

Chain tensioner. It could be seeping from where it mates to the head surface. There's a crush washer under there and oil could be running down and then get dispersed all over the alternator and other parts.

Mine began to leak on my '93 300D and the oil coverage looked just like that. I'd bet a dollar to a donut that that is where your leak is coming from. Then again, I could be wrong.

Remove the tensioner, lightly sand the crush washer on both sides, follow the FSM tensioner printing procedure with engine oil, and reinstall with a torque wrench to the FSM torque.

__________________
'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
http://badges.fuelly.com/images/sig-us/302601.png
http://i959.photobucket.com/albums/a...0/sideview.png

That's the coolant temp sensor for the glow relay. The temp sensor goes into coolant, not oil. so the leak is elsewhere. Could be the chain tensioner just above as mentioned but that's a 2.5 so a failed head gasket is a usual suspect.

Sixto
83 300SD

Any oil leaking from the front of the motor ends up here, thanks to the fan. Check for a leaky pan or front main.