OM651 engine knock

[ZHQ1]

I have a 2015 C220d. My car has a slight knocking sound from the engine.
Here is a video of it.

It only appears when the engine is cold occasionally
Very slight knocking sound from the middle of the engine
and the sound disappears after half a minute, is this normal?

 

[alexanderfoti]

Very hard to tell from video, sounds mainly like combustion noise, which would explain why it goes away after 30 seconds (Which rod knock wont do!)

 

[ZHQ1]

Very hard to tell from video, sounds mainly like combustion noise, which would explain why it goes away after 30 seconds (Which rod knock wont do!)

Hope it's not a big problem, tried a cold start today, didn't catch the sound, it seems to go away

 

[ajlsl600]

Dodgy injector. My guess. Get it on diagnostics drop injectors 1 by 1 see if issues goes on particular cyl. Get injector serviced or replaced if req

Miss behaving cam sensor if applicable.