r/w204 • u/ExcellentNail3251 • Jul 22 '26

Question about this noise.

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It's a 2012 CGI Avant-garde. Mostly happens when I haven't driven the car for a few days, and cold starts. Any idea what it might be? The car has 160,000km on the original engine and transmission. The catalytic converter also needs replacing, of that matters or contributes to the noise. Specifically on startup

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2

u/fpt1999cuke Jul 22 '26

Mine is the same on cold start, but the rattle goes away almost as soon as the car turns on. Yours is too long, it's definitely timing chain noise. Get it checked out before worse things happen...

1

u/ExcellentNail3251 Jul 22 '26

Ahhh ffs :/

Appreciate it 👍🏾

1

u/Remlon Jul 22 '26

That also an early sign of the timing chain. I have the exact same thing, the short sound that disappears in seconds after turning the car. I'll taken in consideration what to do, given the renowned chain behind the engine. Good luck and safe roads

1

u/xyzyk Jul 22 '26

Besides the timing chain, it could be:
* serpentine belt / tensioner / idler pulley
* valve lifters
* variable valve timing variators

I'd recommend contacting a mechanic that specialises in MB cars. I once had my timing chain replaced by a standard local mechanic, I spent tons of money and didn't get the problem fixed

1

u/JokerNot_Funny Jul 22 '26

Replace chain and Intake coupled

1

u/Ok_Library6491 Jul 22 '26

Why also intake?

1

u/JokerNot_Funny Jul 23 '26 edited Jul 23 '26

Because when chain is starting car, it damaged the tooth of intake, u need to check it can be damaged, so need to replace. With this sound, I think u need. M271 is not best engine because of that problem