diesel woe: rattling noise
 

On my 300D sedan, I am getting a nasty knocking noise from the engine.

sounds like "tang tang tang tang", like metal hitting metal. It increases in speed with engine speed.

Symptoms:

more apparent when the car is not fully warmed up.

only happens on take off, when engine is under load, but at low RPM. Once cruising over 40 mph, it goes away.

fuel injectors?
could a cracked prechamber make this happen?

chain stretch?

Most likely injector knock, could also be a bad chain tensioner.

While idleing, loosen the cap nut on the injectors one at a time. If the knock goes away when you loosen one, chances are it's a bad injector. If it doesn't, suspect something else.

Sadly, new injectors don't always fix knocking, and if fact can make it worse if something else is the cause.

Low compression from tight valves will also cause knock, so will late injection timing.

Check the timting chain for stretch (do a search) and adjust the valves, too.

Peter