New Sound-Maybe my turbo going?
 

I have been hearing a new sound from the engine compartment on my 84 300D, so I set up a stethoscope with a length of plastic tubing. I put an earplug in one ear and the end of the tube in the other and explored around. At first I suspected the water pump but got nothing from around there. Next was the turbo unit. When I got close in around the top, it sounded somewhat like a small popcorn kernel was bouncing around in there. Could this be a bearing going bad? I have 314K on the car and the turbo unit was replaced a few PO's ago at 117K. Not sure why the original went so early, but if the story is correct, this one has just under 200K on it. My dipstick shows that it is almost ready for a quart of oil and I will add some tomorrow, but I doubt this has anything to do with it. I changed the oil a few thousand miles ago. Anyone have any advise?

What speed were you running the engine at when you were checking?
I have never had the intake elbow off to checked but I do not think the turbo rotates enough at idle to be able to check it. Also when one of the turbines starts rubbing on the housing the turbo is usually noiser as the speed increases.
With the engine off and cold remove the intake between the turbo. Reach inside the turbo intake; grab the nut on the Compressor Wheel and push the Compressor Wheel all the way to the rear of the car as far as it will go. Keep pressure on it and rotate it slowly; feel and listen to see if it is rubbing on any thing. If you can pull it towards the front of the car and do the same thing. Pull it in and out to see how much thrust it has; If you hear or feel a hard "thunk" when you do this the thrust washer/bearing in the turbo may be worn out.
Grab the nut on the compressore wheel push in lightly and put a side ways pressure back in forth and see if the side play also "thunks".

The diagnostics with my "stethoscope" were done at idle. I first noticed the sound at idle as well. I do not hear anything out of the ordinary when traveling at higher speeds. I'll try listening with the engine revved up a bit.

What about a coolant leak, drip hitting the fan?

my engine fan blades were hitting my alternator cooling blades :eek: