What is the cause of engine clacking? I'm thinking finely tuned, these diesels should have a nice purring sound to them, not loud clacking. Mine's not excessively loud, but louder than it should be.

I've purged my lines before and put treatment in the fuel tank. Just wondering if some of this is caused by injectors that are old and maybe not popping at the right pressure or something.

1991 300d 230k

I'd like to understand this myself, had a previous clacker that I never got quiet. Could hear me coming from quite a ways lol!

One thing I remember reading IIRC if it runs quiet during the purge process, is that it is likely injectors?

I remember reading about something with the prechambers also possibly causing clacking.

bad "lifter"?

OM 60X engines exhibit all kinds of noises from the serpentine belt system when that starts to go funky from one part or another.

X2,I have a suspect "engine shock" if you put a long box end wrench on it and add some pressure it quiets down, that or maybe serpentine belt tensioner, haven't looked at that yet.

I don't know if the vacuum pump on yours has the articulating arm or is a rotary one.

Use a mechanics stethoscope or something else like a broom stick applied to the vacuum pump and other places to see if you can here where the clacking is coming from.

What is typically called nailing can be from worn injector nozzles and or Fuel Injection Pump timing.

Then there is that other stuff mentioned by the other members.

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84 300D, 82 Volvo 244Gl Diesel