S-Class (W221) 2007-2013: S 320 CDI, S 350, S 450, S 500, S 550, S 420 CDI, S 600

Rattle sound after start

Old Jan 22, 2025 | 02:24 PM
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Mercedes S500 W221
Rattle sound after start

Hi! Especially 5sec after cold start (when rpm drops to 1200-1000), I can hear strange rattle sound from my engine. After warm start it’s the same thing but quieter and shorter. Any advice? Thanks!

Here’s video:

https://youtube.com/shorts/cvR-1ak7XiM?si=XYqEMBx5RZFk6qX6
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Old Jan 22, 2025 | 04:40 PM
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2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, 2017 Mustang GT, 2023 300C, and a 2019 Lincoln
I may be wrong, but it sounds like one of your catalytic converters has blown. Put the car on a lift and listen from underneath.

Keep us posted.
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Old Jan 29, 2025 | 01:18 PM
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Mercedes S500 W221
Originally Posted by vettebk
I may be wrong, but it sounds like one of your catalytic converters has blown. Put the car on a lift and listen from underneath.

Keep us posted.
Mechanic said that catalytic converters are okay. He can't find out what caused that noise. I’ve just read about some o-ring in oil pump - service guy told me that is the problem with m272, not m273 - I don’t fully trust him. Of course, there’re thoughts about replacing timing chain which cost +-5k € - in my opinion the sound of timing chain appears immediately after the engine starts and sounds a little bit different but I don’t know anything about a cars - my knowledge comes from YT and google
Few days ago I’ve noticed that the noise is quieter but a new symptom has appeared - rattling noise while driving on cold
engine when pressing the gas. After the engine warms up, everything is okay



Last edited by rafrut; Jan 29, 2025 at 01:31 PM.
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Old Jan 29, 2025 | 03:11 PM
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that’s sounds horrible - usually that type of noise is external - almost like an exhaust bracket has separated

if you think that’s inside the engine I'd not start it....
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Old Jan 29, 2025 | 03:25 PM
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Mercedes S500 W221
Originally Posted by BOTUS
that’s sounds horrible - usually that type of noise is external - almost like an exhaust bracket has separated

if you think that’s inside the engine I'd not start it....
Usually it sounds like that: 00:16, 0:03, 0:33


When it happens engine is shaking a little bit
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Old Jan 31, 2025 | 07:01 PM
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Sounds like mine when i had a bad adjuster....get a mechanics stethoscope and put it at the top of the engine on the passenger side by the oil filler....if the sound comes from there its the adjuster....most likely the exhaust one

Good luck.
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Old Feb 1, 2025 | 12:06 PM
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2010 E550, 273 Engine: 2012 S550, 278 Engine
Originally Posted by rafrut
Hi! Especially 5sec after cold start (when rpm drops to 1200-1000), I can hear strange rattle sound from my engine. After warm start it’s the same thing but quieter and shorter. Any advice? Thanks!

Here’s video:

https://youtube.com/shorts/cvR-1ak7X...qEMBx5RZFk6qX6
That sounds exactly the same as I had with my 2013 S550 with the 278 engine. It was the HP fuel pump(s) or the lifters. I don't know exactly what as I replaced them all parts. Rattle comes from the roller lifter bouncing against the cam shaft that runs the pump and will destroy the shaft if let do that for too long.

But in the 3rd post in this thread it indicates your engine is m273. Is that what you have? It does not have HP fuel pumps.
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Old Feb 4, 2025 | 06:29 AM
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Problem solved. I’m not sure if I’m saying it right, but that’s how mechanic explain it to me. Some time ago the v-belt broke down - has been changed. Broken parts of the v-belt were scattered around the engine, which resulted in low oil pressure (the mechanic literally pulled pieces of the belt out of the oil sump). That caused damage to the one element of timing mechanism. I’m sorry if I’m talking bull****, but that’s how I understood it
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Old Feb 9, 2025 | 01:44 AM
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2010 E550, 273 Engine: 2012 S550, 278 Engine
Originally Posted by rafrut
Problem solved. I’m not sure if I’m saying it right, but that’s how mechanic explain it to me. Some time ago the v-belt broke down - has been changed. Broken parts of the v-belt were scattered around the engine, which resulted in low oil pressure (the mechanic literally pulled pieces of the belt out of the oil sump). That caused damage to the one element of timing mechanism. I’m sorry if I’m talking bull****, but that’s how I understood it
Pulling pieces of V-belt out the oil sump sounds Bull•••• to me.
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Old Feb 9, 2025 | 05:16 AM
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On the 273 / 278 engine if the drive belt come off there is no normal way for any of the belt to get inside the engine - but if catastrophic enough - I guess damage to the front cases, silly plastic oil filter lid might occur - one would hope in such instances a bit of effort was made to check. As Arrie suggests, It does sound like some artistic license on the repair just made has been involved in the job description / pricing

But note if you buy certain 2012 to 2019 Ford Focus' bits of belt in the sump - is normal... turns out wet belt cam drive engines (loads these days from Hyundai, PSA and Ford ) don't like direct injection - nor can they cope with ethanol in the fuel - its got so bad Ford has had to pull the wet cam drive, and later revisions of the engine get a chain - but in some lunacy - they kept the separate wet belt drive to the oil pump - and it gets worse. To change the oil pump belt, that is affected by direct injection and ethanol fuels in exactly the same way, you have to take the cam chain off !

turns out direct injection allows too much fuel to get past the rings (to rot the wet belts) - as it doesn’t have the natural bore cleaning of the oil / fuel mist in the chamber before the burn - (a similar issue that drives LSPI of direct injection petrol engines) - all of which is new news, and the same driver behind the release of MB 229.7 oil spec






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