OM642.830 Loud Knocking Then Fine ???


Active Member
Oct 2, 2017
The Titanic
I have a 2010 c350 cdi with 0m642.830 engine, i have had a light tapping noise for around 6 months now and recently dpf issues and intermittent smoking after idle

Today i got a code saying its trying to Regen the dpf too often so cleared the code and took it for a run to regen and blow it out.

Temps came up as expected but half way through my run out i got a horrendous knocking noise that sounded like a tappet had exploded, i slowed down gently and had weird response form the throttle and random revving of the engine .

Once stopped i notice my oil temp was around 120 degrees ans lifting the bonnet some smoking from behind the turbo, i restarted the engine and the knocking noise was gone along with the original tapping.

I had a very easy drive home letting everything cool down.

Upon starting again i had smoke form my offside rear tailpipe only blue\white, took it for a gentle run and this cleared up no issues

tapping completely gone, had another run to the supermarket later and wen i stopped and gently revved the engine i got smoke again form the offside tailpipe only, drive home was fine no smoke no issues

I have zero power loss and no tapping, knocking at all now.

I am wondering if i have had a bad tappet that finally given up hence no noise now.

Could a bad tappet cause smoking and or DPF issues ?

I have ordered two MB tappets for my engine and think i will pull the left valve train to see if i can see any issues as this is where the tapping came from.

If anyone has any insight into this it would be great, i am concerned what damage may have been done with that awful noise i got earlier


MB Enthusiast
Aug 9, 2012
W212, C219
Yes, leaking (in cylinder) injector often cause a loud knocking.

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