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C270 engine noise

Fabill

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Joined
Apr 6, 2010
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I have recently bought an 05, C270 Avantgarde with 32K miles. The car is in such brilliant order that I wasn't really paying much attention to the engine sound during the test drive - the route, anyway, was pretty flat and wouldn't have highlighted this issue. However, after a few hundred miles this has definitely become an issue. The background throbby sound is quite pleasant; the performance is more than adequate but both of these aspects are subordinated by a chattery noise under light acceleration, replaced by a tappety sound in syncro as the revs rise under hard acceleration.
So, to get to the point. A search reveals one or two members with similar experience but, unfortunately no one lists the cause/cure?
It really is a pity that the noise is so intrusive, as the car, otherwise, ticks all of the boxes for me. It's also a brilliant looker IMO.
 
Is this a CDI engine you're talking about?
 
Its normal... Mine chatters with light throttle and growls when pushed hard. What you will notice is how it quietens down when properly warmed which is a rare occurance as they run very cool.
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When was the oil last changed, and does the service book say what was used?
 
Its not so much an engine chatter more injectors
 
Try running it on a premium diesel such as Shell Optimax.....I find my C270 runs much quieter on this than regular diesel, especially if you have been using Supermarket Diesel.
Alternatively try adding a dose of Millers diesel Power addative to Regular diesel...this tends to have the same effect in my experience (but still avoid Supermarket Diesel...stick to the main brands...Shell, Esso, Total, BP)
 
I find that CDI's are more noisy than the old type of diesel anyway but I will give your sugestion a try
 
Its normal... Mine chatters with light throttle and growls when pushed hard. What you will notice is how it quietens down when properly warmed which is a rare occurance as they run very cool.
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Update.

I'm getting used to the "throbby" sound - quite pleasant, actually- and can live with the "chattery" sound - this is only present on light throttle. Both of these, I assume, are related to the combustion process itself. But it's the distinct mechanical "tapping"sound that is irksome.

When cold it sounds exactly like the tappet noise you used to get from over head valve engines when the clearance on a single tappet was excessive. Also, as was the case with those engines, when warmed up the sound recedes but is still there under hard acceleration. I've no knowledge of the 2.7 diesel engine valve gear so don't know if there's such a thing as a tappet. However, there's definitely something which is causing this infernal "tapping" sound and I'm disappointed that this should be present in a car with 30K miles from a premium manufacturer such as Mercedes. Previous car had the VAG 1.9 TDI PD engine and that was much more refined with no hint of mechanical sounds, whatsoever.

Having said all this, I'm still impressed with the overall package and look forward to the day when this noise issue is a thing of the past.
 
Try running it on a premium diesel such as Shell Optimax.....I find my C270 runs much quieter on this than regular diesel, especially if you have been using Supermarket Diesel.
Alternatively try adding a dose of Millers diesel Power addative to Regular diesel...this tends to have the same effect in my experience (but still avoid Supermarket Diesel...stick to the main brands...Shell, Esso, Total, BP)

Thanks. I'll give Optimax a try.
 
When cold it sounds exactly like the tappet noise you used to get from over head valve engines when the clearance on a single tappet was excessive.

Maybe that's what it is. The cars have hydraulic tappets and there have been other reports of the odd one becoming noisy.
 
Latest:

Premium fuel. Recommendation from here, Optimax (BP Ultimate, actually, for last 4 fills). Unfortunately, no apparent change in noise.

Visit to dealer to get opinion - quote, "that's the way the 270 engine sounds, so, no worries, the engine is fine."

Oil change from 10w40 to 5w30 - MB 270 owner said that should help with reduce in the "noise". No change.

Patience has run out. She's going this week. Such a pity, really.
Apart from the engine noise - Oh!, and the achy right leg syndrome, as well - the car is a credit to Mercedes engineering.
Terrific: ride; cabin design; equipment levels; performance; appearance....etc.
 

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