Aussie_E350_Wag

My E350 does this dull knock knock knock sound on cold starts, after sitting over night, not every time but occasionally. My mechanic friend said it's most likely piston slap on start up, he said my engine has 170,000km on it and it's not unusual for its mileage.

Yours is much newer so I would be very concerned it's getting this noise on start up.

Robert L

Hi there, I just noticed my car making exactly the same noise on start up. Goes away after 3 to 5 seconds. Doesn't make this noise every time just occasionally. Do you know what it was?

Robert L

did you get the knocking issue identified. No one knows what it is and my car has it occasionally as well.

Robert L

No one can tell me what the knocking sound is. My car has it occasionally. Has anyone repaired the issue? Funny thing is it rarely does it on cold starts usually does it when warm or hot after stopping the car for a hour then re starting. It's pissing me off, I'd really like to know what causes it. My engine doesn't suffer from the bad batch of timing chains, balance shaft or guides but still occasionally makes this bottom end knocking for 2 to 3 seconds then goes away as soon as oil pressure comes on. It has to be a oiling issue. I'm almost tempted to stop using expensive oil and putting Castrol magnatec in to see if it stops this knocking sound

gogydm

Many M272 engines exhibit this behavior. My car does it too and it's currently at 195k miles. On an oil forum this problem was discussed and they tried to come up with a solution, as in to what oil to use to not have this issue. Nothing really helped. I have noticed it less with Liqui Moly 5W-40 than the Mobil 1 0w-40 (which I wouldn't put in my car anymore as it burns a quart every 5k or so). It also occurs less than Mobil with the Castrol 0W-40 that is currently in the car. Bottom line was it may be rod bearings and we can't do much other than change those or live with it as it's only for a couple of seconds and not every time.

Robert L

Someone on another forum managed to get Mercedes-Benz to confess that this specific 2 to 3 second knocking sound is actually a titled piston. Apparently almost all m272 engines make this noise randomly at times upon start up. Nothing can be done about it and apparently Mercedes-Benz say it does not cause the engine any harm, and at 215,000km I'd say they are correct. So many new m272 engines under 80,000km and 50,000km reported making this knock so I'd say they may be telling the truth.

E55Greasemonkey

There is a bulletin from MB regarding this sound. The remedy is to replace only the upper half of the crankshaft bearings with a tighter spec clearance bearing. Somewhat of a big job, especially in a 4matic vehicle. With 182k miles on mine, it's not worth the work or expense.

AetherSprite

Do you happen to have a link to that forum thread? My E550 makes this noise on almost every startup. It also occasionally has a quiet "rattle" under moderate to heavy acceleration at ~3k RPM, maybe related? I love this car, but this M273 engine has me concerned.

Robert L

There's conflicting information regarding this, the two main theories are tilted piston and upper crankshaft bearings that were to thin causing the knock sound. I actually believe it's a oiling issue myself as it doesn't do this noise all the time, usually once warmed up and the oil thins out and drains down to the oil pan. I may try a thicker oil 5w30 to see if it helps as my car has always ran a 0w40w

Robert L

your rattle is most likely the camshaft adjusters, they were a common fault as well

dvenneman

First, how many miles do you have on the car? Second, if you are having a rattle that occurs at start up only (as the engine settles to under 1,090 rpm and it goes away within seconds, then you are likely a) low on oil; b) burning oil; c) have some chain wear happening; and d) like me, in for some larger repairs on your car.

I am at 247,600 and this is where I am at. I have at least two valves that are leaking - you can tell this from pulling and inspecting the spark plugs. Mine is a 2007. Unfortunately it is time for me to invest in another vehicle.

Robert L

2007 Avantgarde, 215,000km not low on oil, level is exactly on full mark at all times. The engine uses no oil at all between 10,000km oil changes. Not 1 leak on engine. The dull knock knock knock only happens when engine is warm and oil is hot. Usually 30 minutes to 1 hour after engine is stopped then re started, it does not make this sound when cold. Car has had oil changed every 10,000km by mercedes since new. My engine is not affected by the soft timing chain or tensioner and balance shaft issue's either. If it were bad chain or tensioner it would make this noise every start up and while running, the engine is as quiet as a mouse.

AetherSprite

Just drove it pretty hard today and I couldn't hear the rattle at all. It only seems to do this occasionally. If you don't mind me asking, how can I confirm the cam adjusters are the source of the sound, and by cam adjusters do you mean the actual adjusters (very expensive if I need to do all four) or just the magnets?

Robert L

cam adjusters would make noise all the time. There's a few videos on this thread with drive train noise and bottom end knocking. If you can find a video that produces the same sound yours is doing that would help. Adjusters are more expensive than magnets. Magnets are a easy change and much less expensive. If you think it's Magnets I'd change those first before anything else

keeepwalking

Hi guys, my mercedes e350 w212 with engine m272 sometimes has the same rattling sound at startup. I hear that noise only for 2-3 seconds and it is more louder after the car has been parked for 3-4 hours. At cold start the sound is almost not noticeable.
It is the same sound as in the clips



Does somebody find a solution?

gogydm

What oil do you have in the car?

keeepwalking

The oil is 5x40 Mercedes Benz 229.5. I changed it recently.

Ehabmj

My car does the same drum noise as this on the video?

linkfosta

I have the same issue with the noise on startup, I replaced with updated tensioner and check valve for the right side. The issue still the same, no improvement..... I turn the engine and found one of the Sprocket solenoid on the intake side is spiting out oil. At this point I don't know what I need to replace. I don't even know how to determine if the chain is no good or not. Or even the sprocket, Anyone can help me? or share some experience?

The whole thing started with engine misfire cylinder 1 (P0301) and now engine shakes at low speed and when you press the gas. I heard this rattle noise is pretty common issue with m276.