C300 engine noise
Senior Member
Joined: Feb 2008
Posts: 300
Likes: 2
From: Toronto
2008 c300
Some Lexus had a knocking sound, caused by the variable valve mechanism.
MBWorld Fanatic!
Joined: Feb 2004
Posts: 3,986
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From: SEATTLE WASHINGTON USA
'08 C300 Lux Barolo Red Beige Leather P2 MM 18" wheels '84 944
The dealer says its normal because Mercedes tells them to say its normal because no harm is going to be done to the engine its just an annoying noise. The knocking sound is from the upper main bearings, theres not enough oil pressure built up during the first couple seconds of startup. The fix is to remove the old bearings and replace them with one size bigger bearings to help build pressure as soon as the engine starts. Ive heard this noise in several 204's including a 2011 with less than 5000 miles on it that I fixed last week by replacing the bearings. Im just letting you guys know what i've done to fix the problem..
In my previous MBs with M103 and M104 engines (maybe others, can't recall) I heard this noise after every oil change (done by me) but only that one time and not until the next change when the system was empty again.
Same three or four knocks.
I have never heard any of these other noises, "noisy as a Ford Diesel truck" etc. In fact, it's the quietest engine I've ever owned.
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Joined: Sep 2009
Posts: 2,108
Likes: 7
From: Dix Hills, New York
2012 C250 Coupe
Ok, so the knocking on startup is considered a non-issue. However, hopefully we can sort out a few other oddities associated with startup/shutdown.
VERY rarely I get the shudder when turning off the car as if fuel still injected into a cylinder and sets off one or two cylinders, causing them to rotate about a split second after the car is turned off causing an unpleasant sound and feeling in the car.
But, more often, and no one else has complained of this to my knowledge, when STARTING the car, it sounds like it is about to die before it turns over and starts. Not a sound related to a dead battery, but a sound that I would describe as though the timing is off and it creates a rough start. Then all goes to normal after a few seconds... It seems to happen randomly, but bundled together. Meaning 3 starts is a row, cold, hot, it will startup roughly, and then start 50+ times after than normally.
Lastly, even after the vehicle is warmed up, sometimes at idle, but more often when dirivng (even at constant speed or RPMS) I get a bouncing of the RPM needle. Does anyone else have this issue? I understand that it is normal for this to occur when you first start up, but I have never had it continue to happen even after drivng for a long time.
VERY rarely I get the shudder when turning off the car as if fuel still injected into a cylinder and sets off one or two cylinders, causing them to rotate about a split second after the car is turned off causing an unpleasant sound and feeling in the car.
But, more often, and no one else has complained of this to my knowledge, when STARTING the car, it sounds like it is about to die before it turns over and starts. Not a sound related to a dead battery, but a sound that I would describe as though the timing is off and it creates a rough start. Then all goes to normal after a few seconds... It seems to happen randomly, but bundled together. Meaning 3 starts is a row, cold, hot, it will startup roughly, and then start 50+ times after than normally.
Lastly, even after the vehicle is warmed up, sometimes at idle, but more often when dirivng (even at constant speed or RPMS) I get a bouncing of the RPM needle. Does anyone else have this issue? I understand that it is normal for this to occur when you first start up, but I have never had it continue to happen even after drivng for a long time.
Last edited by jctevere; May 27, 2011 at 03:30 PM.
MBWorld Fanatic!
Joined: Feb 2004
Posts: 3,986
Likes: 6
From: SEATTLE WASHINGTON USA
'08 C300 Lux Barolo Red Beige Leather P2 MM 18" wheels '84 944
Lumpy
Ok, so the knocking on startup is considered a non-issue. However, hopefully we can sort out a few other oddities associated with startup/shutdown.
VERY rarely I get the shudder when turning off the car as if fuel still injected into a cylinder and sets off one or two cylinders, causing them to rotate about a split second after the car is turned off causing an unpleasant sound and feeling in the car.
But, more often, and no one else has complained of this to my knowledge, when STARTING the car, it sounds like it is about to die before it turns over and starts. Not a sound related to a dead battery, but a sound that I would describe as though the timing is off and it creates a rough start. Then all goes to normal after a few seconds... It seems to happen randomly, but bundled together. Meaning 3 starts is a row, cold, hot, it will startup roughly, and then start 50+ times after than normally.
Lastly, even after the vehicle is warmed up, sometimes at idle, but more often when dirivng (even at constant speed or RPMS) I get a bouncing of the RPM needle. Does anyone else have this issue? I understand that it is normal for this to occur when you first start up, but I have never had it continue to happen even after drivng for a long time.
VERY rarely I get the shudder when turning off the car as if fuel still injected into a cylinder and sets off one or two cylinders, causing them to rotate about a split second after the car is turned off causing an unpleasant sound and feeling in the car.
But, more often, and no one else has complained of this to my knowledge, when STARTING the car, it sounds like it is about to die before it turns over and starts. Not a sound related to a dead battery, but a sound that I would describe as though the timing is off and it creates a rough start. Then all goes to normal after a few seconds... It seems to happen randomly, but bundled together. Meaning 3 starts is a row, cold, hot, it will startup roughly, and then start 50+ times after than normally.
Lastly, even after the vehicle is warmed up, sometimes at idle, but more often when dirivng (even at constant speed or RPMS) I get a bouncing of the RPM needle. Does anyone else have this issue? I understand that it is normal for this to occur when you first start up, but I have never had it continue to happen even after drivng for a long time.
Be persistent.
MBWorld Fanatic!
Joined: Oct 2010
Posts: 1,128
Likes: 19
From: Acapulco Mexico
2010 C300 Sport
Upon investigating the characteristics of the MB approved 229.5 synthetic oil, it is surprising to see that they are 0W-30, 5W-30 and 0W-40. More like cold weather oils, perhaps at average temperatures in Austin, this is just too thin at the lower end (Acapulco is also warm, 88°). The crankshaft noise is not present in my C300, perhaps W204's destined for Mexico come with 10W-40 or 10W-50. I even have to pay attention to the tachometer starting up, the engine is so silent, seems like it didnt start, especially with doors and windows closed.
However, since you have a lease, and if the MB dealer isnt concerned, maybe you should just ignore this issue. On the next oil service (and do you pay for this with a lease?) perhaps the MB dealer could be persuaded to investigate if a different "MB approved engine oil" should be used.
However, since you have a lease, and if the MB dealer isnt concerned, maybe you should just ignore this issue. On the next oil service (and do you pay for this with a lease?) perhaps the MB dealer could be persuaded to investigate if a different "MB approved engine oil" should be used.
Newbie
Joined: Apr 2011
Posts: 2
Likes: 0
2011 Mercedes Benz B-Class
Answer to your question
We leased a C300 two weeks ago. Has about 450 miles on it. Since it was new, it has a cold start noise that is troubling. Like it's low on oil. Not really a tappet noise though, more like a bearing noise. Noise sounds "throatier". Goes away in about 3-5 seconds. Only happens in the morning after she sits overnight. Oil level is correct. No other symptoms. We are south Texas so it is hot. Garage gets over 100 degrees regularly. Could it be the timing chain?
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Junior Member
Joined: Jul 2008
Posts: 44
Likes: 0
From: Chesapeake, VA
'08 C300W Lux
Still Whining about the Knock, Knock!
I've been complaining along with others for near 4 years now & 15k later little has changed except my warranty is about to expire. I'm pushing my dealership to do something & it's been there since Tuesday. Finally got them to acknowledge the knock after an overnight stay for a bone cold start. They say my noise is a 3 on a scale of 10 and they all do it. But they don't know what the noise is, it won't harm anything, yada, yada. On a hunch I got them to start 2 used C300's (a '08 with 33.5k) & an '09 with 41k). Neither made the noise. They do say that it's not my Canister Purge Valve. Anybody had any luck getting this problem fixed???? I saw where a couple people have gotten dealers to install refitted bearings (of unknown sort) but have been unable to obtain repair details, TSB's or anything that could be used as ammunition or even assistance.
Last edited by Les-10; May 3, 2012 at 04:40 PM.
Junior Member
Joined: Jan 2012
Posts: 26
Likes: 0
From: N. California
2010 C300 RWD Auto, 2010 Prius, 2013 Porsche 911 Carrera
Anyone had any luck with getting this improved? I have rough engine start/idle when cold and it makes that sputtering "diesel" noise.
My service rep at the dealer said that they duplicated the sound, but (I quote exactly from the message he left me) "it is something that Mercedes does know about, so we do acknowledge it's there. Unfortunately, there is not a correction for it yet."
It seems that Mercedes just want to ignore this problem entirely.
Most W204's seem fine. I wonder what percentage of cars have this annoyance.
Just wanted to keep this thread alive and hope some solution will come up.
My service rep at the dealer said that they duplicated the sound, but (I quote exactly from the message he left me) "it is something that Mercedes does know about, so we do acknowledge it's there. Unfortunately, there is not a correction for it yet."
It seems that Mercedes just want to ignore this problem entirely.
Most W204's seem fine. I wonder what percentage of cars have this annoyance.
Just wanted to keep this thread alive and hope some solution will come up.
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,369
Likes: 319
From: WI
GLK 250
Add me to the list of knock-knock-knocks. Although mine is more noticeable after a 4-6 hour break, not so much overnight. Go figure. I use M1 0w40 Euro Formula, mileage just over 30K.
It's not getting any worse, but if there is something that can be done (short of tearing into the engine) I'm game. Check valve, sensor, whatever.
No warranty for me... I am my own warranty!
It's not getting any worse, but if there is something that can be done (short of tearing into the engine) I'm game. Check valve, sensor, whatever.
No warranty for me... I am my own warranty!
MBWorld Fanatic!
Joined: Oct 2008
Posts: 2,601
Likes: 28
From: Atlanta, GA
2008 C300 Sport 6 Speed Manual, 1953 Chevy Bel-Air, 2015 Audi allroad, 1963 Chevy Apache
I get a few knocks on maybe 1 out of 20 starts. I have asked to have it looked into a couple of times but, as you likely could guess, was told there was not a problem.
I come off warranty in a couple months so I hope mine is at least not bad enough to cost me sometime in the next few years....or that MB has a fix and offers it to all owners that complained during their warranty period.
I come off warranty in a couple months so I hope mine is at least not bad enough to cost me sometime in the next few years....or that MB has a fix and offers it to all owners that complained during their warranty period.
Junior Member
Joined: Jul 2008
Posts: 44
Likes: 0
From: Chesapeake, VA
'08 C300W Lux
They Outwaited Me!
I get a few knocks on maybe 1 out of 20 starts. I have asked to have it looked into a couple of times but, as you likely could guess, was told there was not a problem.
I come off warranty in a couple months so I hope mine is at least not bad enough to cost me sometime in the next few years....or that MB has a fix and offers it to all owners that complained during their warranty period.
I come off warranty in a couple months so I hope mine is at least not bad enough to cost me sometime in the next few years....or that MB has a fix and offers it to all owners that complained during their warranty period.
Senior Member
Joined: Oct 2009
Posts: 291
Likes: 0
From: MD
'09 C350
I get a few knocks on maybe 1 out of 20 starts. I have asked to have it looked into a couple of times but, as you likely could guess, was told there was not a problem.
I come off warranty in a couple months so I hope mine is at least not bad enough to cost me sometime in the next few years....or that MB has a fix and offers it to all owners that complained during their warranty period.
I come off warranty in a couple months so I hope mine is at least not bad enough to cost me sometime in the next few years....or that MB has a fix and offers it to all owners that complained during their warranty period.
Newbie
Joined: Jul 2012
Posts: 2
Likes: 0
2009 C300
I just took mine in to Mercedes of Alexandria. It knocks really bad. I laugh when I see the comemrical on TV about Mercedes and the founder's motto was "only the best". This knock sound is terrible. I've had my car for 1 year now and it's been there ever since I bought it CPO and getting worse
I hope they don't tell me it's normal. If they don't address it I'm filling complaint with NHSTA (which you all should do), and contacting MB of USA and Germany every week and taking into to the dealership until they correct it. I"m not going to let it go until they address it. Yeah that's how annoyed I am right now.
I hope they don't tell me it's normal. If they don't address it I'm filling complaint with NHSTA (which you all should do), and contacting MB of USA and Germany every week and taking into to the dealership until they correct it. I"m not going to let it go until they address it. Yeah that's how annoyed I am right now.
Super Member
Joined: Nov 2008
Posts: 604
Likes: 29
From: SA
2008 C350-Sport-AMG-Active Agility Pack(Not reliable) +Izuzu KB6 3L(It seems Reliable)+Mazda
Noise on startup-A Green Pump somewhere ?
I also fimiliar with this. I tried a method of starting the engine again after parking it in the garage, say an hour later, letting it idle for a minute, to leave thinker oil everywhere.
It did not seemed to help. 72 000KM nothing in engine broke so far.
Is this not related to a pump somewhere pumping air into the exhaust to fool the Green people should they try to measure the exhaust after startup ?
I must say, after my aircleaner was fitted properly(MAF sensor problem) and erratic idle slightly since new(After 1st 10 000Km service), the engine sounds solid and quiet. The MAF problem only show up after the aircleaner was about to fall off from the rear over intake, meaning it was not properly fitted for a very long time(K's).
I actually forgot about this lately, meaning have not heard it again. Engine idles perfect now.
It did not seemed to help. 72 000KM nothing in engine broke so far.
Is this not related to a pump somewhere pumping air into the exhaust to fool the Green people should they try to measure the exhaust after startup ?
I must say, after my aircleaner was fitted properly(MAF sensor problem) and erratic idle slightly since new(After 1st 10 000Km service), the engine sounds solid and quiet. The MAF problem only show up after the aircleaner was about to fall off from the rear over intake, meaning it was not properly fitted for a very long time(K's).
I actually forgot about this lately, meaning have not heard it again. Engine idles perfect now.
Last edited by Moto_Guzzi; Jul 18, 2012 at 02:13 PM.
Newbie
Joined: Jun 2012
Posts: 8
Likes: 0
99 E240 & 96 E230 & 78 280se
Yes Our 99 E240 (140K on odo.) has some sort of "bearing Knock", for a second or so, on startup some times, (hot or cold). Only had the car for a couple of months, and was a bit worried that the engine was developing a problem.
The previous owner had the timing chain replaced (including tensioner and guides), chasing an engine noise on start up.
I have replaced engine oil twice, also tried a well known additive,(made very little difference)
so am going to just keep driving it, as the engine is really smooth and a delight to drive.
The previous owner had the timing chain replaced (including tensioner and guides), chasing an engine noise on start up.
I have replaced engine oil twice, also tried a well known additive,(made very little difference)
so am going to just keep driving it, as the engine is really smooth and a delight to drive.
Last edited by johngelone; Jul 23, 2012 at 09:00 AM.
Super Member
Joined: Nov 2008
Posts: 604
Likes: 29
From: SA
2008 C350-Sport-AMG-Active Agility Pack(Not reliable) +Izuzu KB6 3L(It seems Reliable)+Mazda
Noise disappeared
My C350-engine noise on startup disappeared:
1-They could have fixed something and not told me, I doubt it.
2-I leave bonnot open after parked in garage for boiling heat to escape for half an hour about.
3-I would rather think they changed the grade of oil on the previous service, this sound the most logical to me. I also noticed the other car a b-class engine also much quieter after last service.
1-They could have fixed something and not told me, I doubt it.
2-I leave bonnot open after parked in garage for boiling heat to escape for half an hour about.
3-I would rather think they changed the grade of oil on the previous service, this sound the most logical to me. I also noticed the other car a b-class engine also much quieter after last service.
Junior Member
Joined: Aug 2012
Posts: 21
Likes: 0
From: Florida
2012 C-250 Coupe
Issue after Shutdown
Ok my issue is after the car is off, a few hours after. I happened to go into the garage and heard this "whoosh" kinda noise, almost like the sound from a blow off valve 
except my husband thinks its an electrical issue. I didn't open the hood but it seemed to be coming from the front middle area. This is the first time I have noticed it so I'm not sure if this is normal. I have had the car less than a month, its a 09 C300 6spd manual transmission. It has under 19k miles on it.
Anyone out there familiar with this sound? I am assuming its normal
seems I have not seen any warning lights come on, but I figured I would ask around here and see what you guys think. Thanks
except my husband thinks its an electrical issue. I didn't open the hood but it seemed to be coming from the front middle area. This is the first time I have noticed it so I'm not sure if this is normal. I have had the car less than a month, its a 09 C300 6spd manual transmission. It has under 19k miles on it. Anyone out there familiar with this sound? I am assuming its normal
seems I have not seen any warning lights come on, but I figured I would ask around here and see what you guys think. Thanks
Newbie
Joined: Aug 2012
Posts: 5
Likes: 0
08 C300 sport 6-speed, Mk2 Turbo Diesel Jetta, 03 Whipplecharged Saleen, 2000 M Roadster (sold)
A noise like this after the car has been sitting is because oil over hours makes its way back to the pan out of the head, the noise is there for a few seconds until oil circulates itself back to the head. Any car I have ever owned does this...
My 2 cents and my first post on this forum
My 2 cents and my first post on this forum
MBWorld Fanatic!
Joined: Sep 2009
Posts: 2,108
Likes: 7
From: Dix Hills, New York
2012 C250 Coupe
Ok my issue is after the car is off, a few hours after. I happened to go into the garage and heard this "whoosh" kinda noise, almost like the sound from a blow off valve except my husband thinks its an electrical issue. I didn't open the hood but it seemed to be coming from the front middle area. This is the first time I have noticed it so I'm not sure if this is normal. I have had the car less than a month, its a 09 C300 6spd manual transmission. It has under 19k miles on it.
Anyone out there familiar with this sound? I am assuming its normal seems I have not seen any warning lights come on, but I figured I would ask around here and see what you guys think. Thanks
except my husband thinks its an electrical issue. I didn't open the hood but it seemed to be coming from the front middle area. This is the first time I have noticed it so I'm not sure if this is normal. I have had the car less than a month, its a 09 C300 6spd manual transmission. It has under 19k miles on it. Anyone out there familiar with this sound? I am assuming its normal
seems I have not seen any warning lights come on, but I figured I would ask around here and see what you guys think. ThanksSecondly, if the sound is more like a buzzing, it could be from the auxiliary water pump moving fluid around after shutdown to cool the engine or other components.
Lastly, if it sounds like air, it could be one of two things. A simple cooling fan, or it could be from the throttle blade opening and closing to allow for expansion gases to escape intake manifold (giving a rush/gust of air). Normal feature during engine cool down to prevent a jammed throttle blade according to MB.
Hopefully one of the above describes your scenario. Either way, if you're concerned bring it into MB service since you're under warranty and just mention it to them. If not, try taking a video/audio clip of the issue. It would be much easier to diagnose then.
Junior Member
Joined: Aug 2012
Posts: 21
Likes: 0
From: Florida
2012 C-250 Coupe
A noise like this after the car has been sitting is because oil over hours makes its way back to the pan out of the head, the noise is there for a few seconds until oil circulates itself back to the head. Any car I have ever owned does this...
My 2 cents and my first post on this forum
My 2 cents and my first post on this forum
Thanks for responding, but I don't think this is the issue because it can be hours after having shut the car off and that's when I have noticed the sound...gonna see what MB says and let ya know
Junior Member
Joined: Aug 2012
Posts: 21
Likes: 0
From: Florida
2012 C-250 Coupe
It could be one of a few possible things. Firstly, if you use A/C and the sound is more like an intermittent high pitched beep once every ~30 seconds, that noise is from the A/C coming back to ambient temperatures after the vehicle was driven.
Secondly, if the sound is more like a buzzing, it could be from the auxiliary water pump moving fluid around after shutdown to cool the engine or other components.
Lastly, if it sounds like air, it could be one of two things. A simple cooling fan, or it could be from the throttle blade opening and closing to allow for expansion gases to escape intake manifold (giving a rush/gust of air). Normal feature during engine cool down to prevent a jammed throttle blade according to MB.
Hopefully one of the above describes your scenario. Either way, if you're concerned bring it into MB service since you're under warranty and just mention it to them. If not, try taking a video/audio clip of the issue. It would be much easier to diagnose then.
Secondly, if the sound is more like a buzzing, it could be from the auxiliary water pump moving fluid around after shutdown to cool the engine or other components.
Lastly, if it sounds like air, it could be one of two things. A simple cooling fan, or it could be from the throttle blade opening and closing to allow for expansion gases to escape intake manifold (giving a rush/gust of air). Normal feature during engine cool down to prevent a jammed throttle blade according to MB.
Hopefully one of the above describes your scenario. Either way, if you're concerned bring it into MB service since you're under warranty and just mention it to them. If not, try taking a video/audio clip of the issue. It would be much easier to diagnose then.
Thanks for responding, the throttle blade issue sounds like it could be a fit, but I'm in no way a mechanic, so we'll have to see what MB says. I'll get back with ya!
Newbie
Joined: Aug 2012
Posts: 12
Likes: 0
From: miami fl
C300
c300 cold start
2009 c300 at the dealer today, service manager claims they have put undersize bearings.. needs to know if its top or bottom ??told him car sounds like a piece of junk and I'm very disappointed with vehicle. This is a certified vehicle and I'm not looking forward to tearing down this motor (mileage 47000) hope they can solve this problem quick
Last edited by raspu; Aug 29, 2012 at 08:10 PM.
