xAirr

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E250 CDI BlueEfficiency (2009) (Engine #OM651)
Hello.

I have recently purchased a 2009 W212 CDI BlueEfficiency (145,000 miles) with the engine, OM651 - my first ever diesel - and noticed that it is a bit on the loud side in terms of engine noise. Having come from a silent Lexus IS250 (Petrol), it sounds like a 'bag of spanners' - even when warm.

Any suggestions on how to make it quieter? I looked it up and saw that 2-stroke oil added into the fuel filler cap can help (alongside diesel) - is this safe? If not, what else could I do?


Cheers!
 

Craiglxviii

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970 Panamera Turbo; W221 S500L AMG Line, C215 CL500, W251 R350L AMG Line, plus several more now gone
It is a slightly clattery engine anyway. That's what you get from a 2.2 litre turbodiesel pulling a 2 ton car.

2 stroke oil wont do anything...
 

Westheath

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With a single duplex timing chain its a weak point on that engine, get it checked over for chain rattle.

Also have the mileage checked on MB Star its a popular taxi vehicle.
 

Headhurts

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As others have said quite a noisy diesel but when warmed up and on the move should be much better.

The Lexus petrol engine was always going to be much quieter.

Did you not notice when you purchased the car?


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kid-jensen

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Ml320CDI 2007
Put more sound unsulation on the underbonnet and both sides of the bulkhead.

Has it still got the plastic engine cover?They make a huge difference to the noise, assuming they still have the insulation attached..

I'm sure you're detecting a theme here....diesel engines (even Mercedes ones) are noisy. The reason why some cars have quiet diesel engines is good attention to sound deadening.
 
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xAirr

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E250 CDI BlueEfficiency (2009) (Engine #OM651)
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With a single duplex timing chain its a weak point on that engine, get it checked over for chain rattle.

Also have the mileage checked on MB Star its a popular taxi vehicle.
Mileage was checked with gov.uk and it all adds up. Its high mileage is due to its days working as a company car, not a taxi.


As others have said quite a noisy diesel but when warmed up and on the move should be much better.

The Lexus petrol engine was always going to be much quieter.

Did you not notice when you purchased the car?
Having driven the car for about a week or so, I haven't noticed any changes after it gets warmed up - still the same 'bag of spanners,' haha.

I knew it'd be quieter, but I hadn't thought that there'd be such a difference, having driven my brother's '08 CLS350 CDI and sister's '15 C250 CDI - both of which are much quieter in comparison. Unfortunately, I wasn't able to see the car until I had bought it.


Put more sound unsulation on the underbonnet and both sides of the bulkhead.

Has it still got the plastic engine cover?They make a huge difference to the noise, assuming they still have the insulation attached..

I'm sure you're detecting a theme here....diesel engines (even Mercedes ones) are noisy. The reason why some cars have quiet diesel engines is good attention to sound deadening.
Yeah, the engine cover is still there. Not sure about the attached insulation though, where can I find that?
 

Headhurts

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Mileage was checked with gov.uk and it all adds up. Its high mileage is due to its days working as a company car, not a taxi.



Having driven the car for about a week or so, I haven't noticed any changes after it gets warmed up - still the same 'bag of spanners,' haha.

I knew it'd be quieter, but I hadn't thought that there'd be such a difference, having driven my brother's '08 CLS350 CDI and sister's '15 C250 CDI - both of which are much quieter in comparison. Unfortunately, I wasn't able to see the car until I had bought it.


The 350 V6 diesel is much quieter than the 2.1 engine, I have had both and the difference is pronounced.

You probably should run your car side by side with your sisters I would not have thought there should be much difference.

If there is then a visit to the experts is called for.

Good luck,

Robin




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Westheath

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Empty garage, awaiting new toy :)
Mileage was checked with gov.uk and it all adds up. Its high mileage is due to its days working as a company car, not a taxi.

Ok
But its easy to keep mileage low by clocking before MOT or having can bus blockers fitted.

And approx 65% of the 4 door E and S classes I have looked at over the past 2 years
due to trying to get a straight one for my neighbour, have been tampered with mileage and service wise.
 
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xAirr

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E250 CDI BlueEfficiency (2009) (Engine #OM651)
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Ok
But its easy to keep mileage low by clocking before MOT or having can bus blockers fitted.

And approx 65% of the 4 door E and S classes I have looked at over the past 2 years
due to trying to get a straight one for my neighbour, have been tampered with mileage and service wise.
But if they wanted to keep the mileage low, they'd have capped it at something like 80k, as opposed to letting it go until 145k, by which point it's considered a "high" mileage car.
 

John Laidlaw

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Insulation is on the bonnet underside
 

Mr.M

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w204 2009 250 CDI
Check the engine mounts. Sometimes they may be the source of noise
 

Craiglxviii

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Check the engine mounts. Sometimes they may be the source of noise
No, the engine and wheels are the sources of noise, engine mounts are NVH dampers ;)
 

M80

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2014 639 Viano- 651, 5sp Auto. 2009 S211- 646, 5sp Auto.
Take it to a good Indy and ask his opinion.
Excess noise can come from many components, there are a lot of bearings to wear on the pulley's, alternator, pumps....

If the mileage is correct, even a fair bit higher, it should be able to run without sounding like a tractor.
 


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