My name is Peter I have a 2012 Mercedes E350 4Matic with 103,000 miles and I have been noticing a knocking noise or ticking on a cold start for about 2-3 mins and then it fades away. It's very consistent and I want to make sure it's nothing major. I do oil changes every 3k miles with 5w-40 liqui moly. I assumed it was chain tensioners, or cam adjusters. Apparently not because if it were chain tensioners or cam adjusters it's only supposed to last a few seconds. If anyone has any idea or advice on what it could I'd appreciate it a lot. Thank you in advance. Video of the sound is in the post.

 

That is not the famous startup rattle...
The cyclical knock says it's from a single cylinder.

It sounds like a rod knock.

Eventually this will get flagged by CEL as a MISFIRING fault code. A degraded cylinder with working ignition.

Are you familiar with oil analysis? You can collect an oil sample and get it analyzed for wear particles.

 

Yes I did an oil change today and collect a sample waiting on the sample kit from black stone to send out and get analyzed.

 

There is a service bulletin for knocking in crank assembly, the remedy is to replace pistons with wrist pins, rod bearings, and connecting rods. I’m just finding it so hard to believe if that is the issue though.

 

I don't know if this level of piston repair will cost less than chassis value.

> PLAN B :
is a viscosity upgrade + drive into the groung gently or shortly.

Have a look at cylinder walls. Some of these engines suffer from oiling issues.
🤞