Have an '85 300 D turbo, and driving home yesterday while accellerating from a stoplight I heard a loud clatter around 3500 rpm... I backed out a little and the noise went away. I stopped and re-started engine and it started and sounded fine... Accelerated again and the noise repeated.
When I got home I put it in drive and revved engine to about 3500 rpm and a lot of grey smoke came out...
What do you think is wrong?? Did I loose an injector or something worse??

Thanks;

Rod

 

Anybody??

 

Unfortunately there is not enough info to give an answer.
It could be something as simple as your Air Filter Housing/Bracket/bushings being loose/broken (when it it happend to me I though something was going to come off of the Engine it made that much noise).

It could also be a Vacuum Pump or Timing Chain/Tensioner failing but there is not enough symptoms to nail it down.

A lot of Gray smoke when you rev the engine as you said you did could be a worn Engine (how many mile on your car) are Injectors needing work but that is not conclusive either as a Restricted/plugged Air Filter might have a similar issue.

Some people have had things get loose like their Engine Fans, Various Drive Pullies and even the Cranckshaft Pulley/dampener.
Are you using only Diesl Fuel?

 

Thanks

 

Might want to check your Pullies and Fan to see if anything is loose. I have to 2nd the loose Air Filter Housing; due to looseness, broken mount or rubber bushings.
When the Air Filter Housing rattles it sounds like yor Engine is going to fall apart.

If your Motor Mounts are collasped it might be possible for the Fan Blades at high speed make conatact with something.
I had somethin similar happen on an old truck. At high revs the Fan Blades bent backwards slightly and would hit the Cranshaft Pulley. I cured it bey spacing that fan out further. But, this vehicle had no Fan Shroud on it (being made in 1953).
Try to pay attention to if the sound is really coming from up front or from under where the transmission is.

Grey smoke. Old engine low compression, plugged/restricted air filter, Injectors need rebuilding, Fuel Injection Pump Timing, sticking Piston Rings (happen to me, I got hazy grey smoke all the time but on a non Mercedes Diesel) and valves need adusting. Just think of all that would make your fuel burn cleaner.