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I have been performing a great deal of research on an issue that seems to be common with the M272 engine.
I bought this car about 4 months ago with 80,000 miles on it. All service records done at Mercedes Dealership to date, perfectly on time. I noticed a low knocking noise (not the high pitch ticking noise that is normal) so I decided to do some investigating. What I found seems to be a somewhat common issue. I have seen a TSB, with audio files attached, that exhibit my symptoms. The TSB's state that the knock is due to "cylinder scoring". I am coming to all of you for a second opinion.
Below is a link to a video of my engine bay while this low frequency knock is occurring. Although this issue seems to be posted all over Youtube, the comment sections aren't very helpful.
I am wondering if the TSB is correct in diagnosing this sound? Is this going to eventually cause engine failure if I continue to drive it this way? How do I fix this issue?
Hi, my C350 was silent till it went for the 1st service. The dealer changed the oil and a thousand or what Km's later I noticed a knock at startup that quickly goes away however not always I hear it, only sometimes. It also developed the singular ticking noise on one side of engine(not the normal finer ticking noises) which to me sounds like a cam follower at idle warm only, it maybe an oil galery design problem starving the camfollower a bit at idle, none of these got worse. I use 229.5 oil supplied by Merc dealers coming from Germany, it maybe recycled oil, because can is not properly sealed like other oil cans you buy at stores. I think I am going to try Shell 229.5 5W-40 as suggested soon. So far 145 00Km nothing broke. I noticed similar complaints on youtube but engines sounds worse than mine.
Your car is as good as the 1st dealer that touches it.
Last edited by Moto_Guzzi; 04-23-2019 at 12:28 PM.
My car has this low-frequency knock, only when warmed up. You can only really hear it when in a drive through or close to a wall. It's been like that ever since I had it, over 120k+ and the knocking has not gone worse (242k on the odo now) I researched it when I first got it (Checked down each spark plug hole with a boroscope camera for signs of cylinder wall scoring, none were found)
Here is a video of a GLK with the same pitch noise but seems a lot worse. I have seen quite a few GLK350s around my area with knocking as shown in the video, it seems the m272, 3.5L engine suffers from some kind of design flaw with the internals of the engine since so many of them have this noise. There is a TSB for 2010-2013 GLK350s with the m272 where apparently, cylinder scoring causes this issue.
Again, my C300 knock is far less than this video, it's so faint that you can barely catch it on video hence why its hard to find a demo video. Unless your engine sounds like the GLK in the video and only hear a light knock when warmed up next to a wall, I won't lose sleep over it, it's normal with these m272 engines.
Last edited by W204Motorsports; 04-24-2019 at 07:16 PM.
My car has this low-frequency knock, only when warmed up. You can only really hear it when in a drive through or close to a wall. It's been like that ever since I had it, over 120k+ and the knocking has not gone worse (242k on the odo now) I researched it when I first got it (Checked down each spark plug hole with a boroscope camera for signs of cylinder wall scoring, none were found)
Here is a video of a GLK with the same pitch noise but seems a lot worse. I have seen quite a few GLK350s around my area with knocking as shown in the video, it seems the m272, 3.5L engine suffers from some kind of design flaw with the internals of the engine since so many of them have this noise. There is a TSB for 2010-2013 GLK350s with the m272 where apparently, cylinder scoring causes this issue.
Again, my C300 knock is far less than this video, it's so faint that you can barely catch it on video hence why its hard to find a demo video. Unless your engine sounds like the GLK in the video and only hear a light knock when warmed up next to a wall, I won't lose sleep over it, it's normal with these m272 engines.
Hi Itwargssf,
My C350 M272 3.5L engine makes the same exact noise. Sounds like it is coming from the 3rd cylinder on the passenger side closest to the cabin of the vehicle.
It makes me feel better that you have driven many miles with the symptoms I am experiencing. I am mostly interested in finding out if this will eventually turn into a major issue years from now.
The TSB that describes this issue calls for a new engine to remedy the problem. Seems extreme if the issue isn't fatal to the engine.
Im bumping this topic because I’m having the same issue with my CLS 350. I think I have found the solution. There was a big discussion about this knocking noise problem in a German Mercedes mechanic forum. But I’m not sure if you are ready for this because it’s a big one...
Im bumping this topic because I’m having the same issue with my CLS 350. I think I have found the solution. There was a big discussion about this knocking noise problem in a German Mercedes mechanic forum. But I’m not sure if you are ready for this because it’s a big one...
Alright, so a german Mercedes mechanic discovered this problem and its actually a well known problem but Mercedes tries to cover it up as good as possible. Its a tilted piston. Mercedes USA actually has a document about this problem. Mercedes says there is nothing you can do about it. They say the only fix is a new engine. So thats the bad news. Its a titled piston that is constantly knocking on the cylinder wall. However the good news is that the engines seem to last really really long with this problem. So a complete engine failure is not very likely. The mechanic said he disassembled countless M272 and the majority of them had indeed a tilted piston and damaged cylinder walls.
I have heard about the scored cylinder walls too. I realize that there isn't really anything I can do. Hopefully the engine lasts. Its been about 20,000 miles since I've noticed the noise, and nothing about the car has changed. So far so good. Thanks for the insight.
Alright, so a german Mercedes mechanic discovered this problem and its actually a well known problem but Mercedes tries to cover it up as good as possible. Its a tilted piston. Mercedes USA actually has a document about this problem. Mercedes says there is nothing you can do about it. They say the only fix is a new engine. So thats the bad news. Its a titled piston that is constantly knocking on the cylinder wall. However the good news is that the engines seem to last really really long with this problem. So a complete engine failure is not very likely. The mechanic said he disassembled countless M272 and the majority of them had indeed a tilted piston and damaged cylinder walls.
Yeh my engine went out a 285 000km and it was an issue with the timing chain that caused the failure and not the titled piston as you say( It knocked ever since I got it at 115 000km) . My replacement engine (3.5L from 2012 GLK350) has the same tapping noise and it was a 70 000km engine. My friend has a 2012 c300 and it also does it. At this point I assume they all do it and its a normal thing that doesn't affect the performance of the engine. The 3L original engine that failed at 285 000km was inspected for cylinder wall scoring and there were none.
Last edited by W204Motorsports; 10-11-2020 at 02:12 PM.
My CLS actually had the entire engine redone like 30.000km ago. The typical balance shaft problem. Since we have the best equipment here at Brabus the cylinders have been honed as well so Im really surprised that I still have this problem. But apparently there is nothing you can do about this problem. Besides the noise I haven't noticed any problems. The car runs smooth and powerful as it should. I will try thicker oil in the future. Some people said the noise got better with thicker oil so lets try it. Other than that I will drive the car until the wheels fall off
Yeh my engine went out a 285 000km and it was an issue with the timing chain that caused the failure and not the titled piston as you say( It knocked ever since I got it at 115 000km) . My replacement engine (3.5L from 2012 GLK350) has the same tapping noise and it was a 70 000km engine. My friend has a 2012 c300 and it also does it. At this point I assume they all do it and its a normal thing that doesn't affect the performance of the engine. The 3L original engine that failed at 285 000km was inspected for cylinder wall scoring and there were none.
I mean almost 300.000 km is quite a lot. What exactly was your problem? Usually the timing chain problem makes itself noticeable long before anything bad happens. However like I said there seems to be a document by Mercedes USA that is specifically about the knocking noise problem. And they suggest a new engine. But when your cylinder walls were alright after 285000 km im not to worried about mine at just 174.000 km lol
I changed to the shell 5W-40 oil recently and this then I never heard it on cold startup again, I did hear it on warm startup after driven 30Km and parked for an hour downhill with the front. The symptoms had changed. As I said before this one was quite till the dealer switch to another oil on 1st service, they had honest service manager and he informed me about CPS(Recall or bullitin) change and the oil.
On my car this low frequency knock was intermittand throughout the year on cold starts, however sometimes it will not do it for a few months, probaly during winter. Originally it had mobil-1 in it after initial inspection from factory change. THen I assume they changed it to this German oil in grey unsealed cans supplied and sold to me, for me that could have been reforbished oil from Germany who knows, the cans were nor properly sealed like any other can you buy.
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In my case I nver ever hear this sound when the engine is idleling or running, after the initial few 3 seconds had passed when it was present or not.
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I am not sure if I should change to a 10w-40 oil, I know 25W-40 would be out of the question, it would just make the starter turn slower.
Note:Mercedes was the 1st car I bought that left a bitter taste behind, I thought I did my homework before buying, no other car so far. The B170 we had had not such issues, a very stable engine it had-I sold it to buy a Pickup to travel gravel roads.
Last edited by Moto_Guzzi; 10-12-2020 at 04:06 PM.
I have a 2011 ML350 with the same tapping noise on idle when warm.
some forums suggest it is a lifter noise, some think the oil tubes for piston lifters are clogged and suggest adding Liqui Moly Hydraulic Lifter Additive to stop the noise.
but nobody can say for sure what causes this tapping noise, all I know is that A LOT of these engines have this inherent problem.
any new information on this?
04-22-2019, 04:56 AM
