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not even a difference there. That is the exact sound, and goes away after the same amount of time. Just replaced the chain tensioners. Same sound. What do you guys think? Check valve? Camshaft adjuster?
I had the same sound on cold startup in my M278 at 30k miles. I knew it was the timing chain from experience and use of my stethoscope on the front timing cover. I then insisted the dealer check it out.
They originally said it was normal operating sounds of direct injection. Then blamed the wastegates on the turbos.
They ultimately replaced the tensioner assembly and added a check valve to reduce drain-back and that fixed the problem.
You cant tell them what the problem is though. They have to discover it on their own I guess.
I did learn something from the whole ordeal... I saw on the invoice something i never heard of before, They replaced things called "Hexolobular" bolts. Or TORX head bolts as to you and I
Dependent on engine # check valves may need to be replaced in addition to tensioners, see attached bulletin.
Apologies for the late reply. I’ve installed the upper tensioners along with check valves, same noise. Doing the bottom tensioner tomorrow along with the check valve of course. My engine number falls under 2769, clause 1. Hopefully this will fix it, however we are going to inspect the camshaft as that has also been a known issue for this sound. Check engine light is now coming on. It goes off and on. I have a GPS tracker that will tell me the code of the engine light. The first few times, it said that it was the camshaft Position sensor A on bank two. Now it is no longer giving me information, leading me to believe another thing is now causing the light.
On other cars when I hear a similar noise I don't suspect the engine, but metal. Like something hitting heat shielding, like the exhaust. When the eng starts it spins up above normal idle, then settles back down in rpm but the fuel is mix is not right so it shudders causing things to touch that don't normally touch. So I'd start it with the hood open and be ready to locate it. If that's the case I then bend whatever so it doesn't do it anymore. Not saying it's not the chain, but that's awfully loud for a chain and classic for heat shield to exhaust.
Optionally, new motor mounts may cure it too since apparently Benz mounts fail sooner than regular mounts, and loose mounts allow more eng movement to cause probs like that.
My chain makes a wee little noise in comparo, like <1% of yours, and it sounds like you'd expect a chain to sound. It was buggin me so I put in 32oz of Lucas Oil which quieted it way down. Quieted the motor as whole down too
I have no idea if mine has the tensioner mods or not (chart says mine is the same as yours).
Please post with details after you dig in deeper b/c I'm really curious...
On other cars when I hear a similar noise I don't suspect the engine, but metal. Like something hitting heat shielding, like the exhaust. When the eng starts it spins up above normal idle, then settles back down in rpm but the fuel is mix is not right so it shudders causing things to touch that don't normally touch. So I'd start it with the hood open and be ready to locate it. If that's the case I then bend whatever so it doesn't do it anymore. Not saying it's not the chain, but that's awfully loud for a chain and classic for heat shield to exhaust.
Optionally, new motor mounts may cure it too since apparently Benz mounts fail sooner than regular mounts, and loose mounts allow more eng movement to cause probs like that.
My chain makes a wee little noise in comparo, like <1% of yours, and it sounds like you'd expect a chain to sound. It was buggin me so I put in 32oz of Lucas Oil which quieted it way down. Quieted the motor as whole down too
I have no idea if mine has the tensioner mods or not (chart says mine is the same as yours).
Please post with details after you dig in deeper b/c I'm really curious...
Update: As I was expecting, the car finally threw a code. Camshaft adjuster bank 2 position A. Common cause of the rattle. I am buying the plates to lock the camshaft down and see which one is the problem. Secondary tensioner has nothing to do with the rattle.
I'm baffled at how the cam adjuster dealie could make that sound. I mean that's a lot of noise for something muffled by all that aluminum, so the actual noise would have to be insane. I can't picture an internal part making that much noise and still work..
If it were bad, and making said noise, would it not continue to make the noise at idle? Why would it be quiet at first, make noise for a couple seconds, then go quiet again until restarted?
I'm not saying it isn't b/c I don't know, but I'm still betting it's the motor shaking. I'm on the edge of my seat either way... If it is this cam thingie I'd love to see pix of it, and your thoughts, so I can wrap my head around the how & why.
I'm baffled at how the cam adjuster dealie could make that sound. I mean that's a lot of noise for something muffled by all that aluminum, so the actual noise would have to be insane. I can't picture an internal part making that much noise and still work..
If it were bad, and making said noise, would it not continue to make the noise at idle? Why would it be quiet at first, make noise for a couple seconds, then go quiet again until restarted?
I'm not saying it isn't b/c I don't know, but I'm still betting it's the motor shaking. I'm on the edge of my seat either way... If it is this cam thingie I'd love to see pix of it, and your thoughts, so I can wrap my head around the how & why.
Best of luck!
Believe it or not, it’s actually a common cause of the problem. I see it all the time. I’ll update when it is fixed. And also, another thing that makes me believe it is that. I changed the oil in the car after it was sitting for three weeks in my shop. Started the car, not a noise. Later that day after leaving it off, the noise is back. This tells me that is a problem with the camshaft because the fresh oil primed the camshaft when changing it, and no noise. Once it drained, the noise came back. Keep in mind the car hadn’t been started in weeks.
on M276 engine, it's the chain tension that causes the rattling because of low oil pressure before the standard oil pressure can be built. remedy is to plant an oil check valve into oil input hole and have the tensioner replaced.
on M276 engine, it's the chain tension that causes the rattling because of low oil pressure before the standard oil pressure can be built. remedy is to plant an oil check valve into oil input hole and have the tensioner replaced.
Don’t believe this is correct. i switched the position sensors for the camshaft adjuster and it throws the same camshaft adjuster code. This car has already had tensioners and check valves replaced. So this is definitely a camshaft adjuster. I’ve seen multiple people say the camshaft adjuster is bad. I bought the tools to lock the camshaft in place to see which one is bad.
Don’t believe this is correct. i switched the position sensors for the camshaft adjuster and it throws the same camshaft adjuster code. This car has already had tensioners and check valves replaced. So this is definitely a camshaft adjuster. I’ve seen multiple people say the camshaft adjuster is bad. I bought the tools to lock the camshaft in place to see which one is bad.
do not think of how the fail tensioner can create kind of metal knocking noise
i begin to agree with you, it's b/c of the camshaft. i opened up the cam cover last week, removed the tensioner only to find out that my engine already has a check valve in the hole. So I just replace a new tensioner. First start is perfect, no rattling. then it came back as it was.
i begin to agree with you, it's b/c of the camshaft. i opened up the cam cover last week, removed the tensioner only to find out that my engine already has a check valve in the hole. So I just replace a new tensioner. First start is perfect, no rattling. then it came back as it was.
Yep. Camshaft adjuster is the cause. This is an extremely common problem. I’ve replaced the check valves and tensioners as well. I switched the sensors and the code remained the same, meaning that the code is correct for a camshaft adjuster, and not a failing sensor.
Yep. Camshaft adjuster is the cause. This is an extremely common problem. I’ve replaced the check valves and tensioners as well. I switched the sensors and the code remained the same, meaning that the code is correct for a camshaft adjuster, and not a failing sensor.
Have you fixed this yet? I have the same rattling sound on warm start up. Extended warranty fixed the chain tensioner and check valve but the noise is still there. Now check engine light turns on for a bit then turns off. I was able to read a P0346 from my scanner. Shop says to change the camshaft adjuster but warranty will not cover it due to timing is not off. I have been following your posts to see if you got it fixed.
Have you fixed this yet? I have the same rattling sound on warm start up. Extended warranty fixed the chain tensioner and check valve but the noise is still there. Now check engine light turns on for a bit then turns off. I was able to read a P0346 from my scanner. Shop says to change the camshaft adjuster but warranty will not cover it due to timing is not off. I have been following your posts to see if you got it fixed.
I have not yet fixed it but I plan on doing it soon. First I want you to know, is that it will not damage your engine. My car has been doing it for over a year. I had the chain tensioner and check valve replaced as well with no change. P0346 is what I have as well. That is the camshaft position sensor. I switched the sensor to see if it was possibly a bad sensor, and the code still persisted for the same engine bank, telling me that the sensor is correct in detecting an issue on that side of the bank. Mercedes will charge you thousands to do this job. I recommend buying the adjuster yourself and having a shop install it for a total of 6-7 hundred. You will need to buy a kit that locks the camshaft down in order to tell which adjuster is bad. You could do it yourself, the only issue is keeping the car completely stable so you don't throw the timing off and send a rod through your engine block.
I have not yet fixed it but I plan on doing it soon. First I want you to know, is that it will not damage your engine. My car has been doing it for over a year. I had the chain tensioner and check valve replaced as well with no change. P0346 is what I have as well. That is the camshaft position sensor. I switched the sensor to see if it was possibly a bad sensor, and the code still persisted for the same engine bank, telling me that the sensor is correct in detecting an issue on that side of the bank. Mercedes will charge you thousands to do this job. I recommend buying the adjuster yourself and having a shop install it for a total of 6-7 hundred. You will need to buy a kit that locks the camshaft down in order to tell which adjuster is bad. You could do it yourself, the only issue is keeping the car completely stable so you don't throw the timing off and send a rod through your engine block.
Thanks for the update. Yeah MB dealer asked 4 grand to fix it. I'll start shopping around for indy shops who will do it. I have 130K miles on the engine thou. Just bought this ML350 and didnt notice this rattling sound since it sounds starts fine during cold and hot start up. Only when the engine is warm after it rested for 20-30 minutes.
Thanks for the update. Yeah MB dealer asked 4 grand to fix it. I'll start shopping around for indy shops who will do it. I have 130K miles on the engine thou. Just bought this ML350 and didnt notice this rattling sound since it sounds starts fine during cold and hot start up. Only when the engine is warm after it rested for 20-30 minutes.
Ah, I see. You’re in the early stages. Mine was like this. At some point it will start getting louder and more frequent. It also won’t matter the temperature. I’ll definitely update everyone once it gets fixed.
Jumping into this thread as I am about to take this journey. 2013 E350 w just a tick over 80K on it. Car has always had the faint cold start rattle. Threw a code for Bank A/Cam 1 just after some longer start times noticed.
Symptoms progressed after the initial CEL:
Hard start, but started everytime (About 10X short <5 mile errands).
Last warm start emitted a louder than normal 'chain-slap' sound that cleared in seconds.
Driving home (less than 3 minutes) the car started misfiring but no other sounds to note.
Changed out the sensors noted with the CEL, cleared CEL car ran flawlessly for about 10min. Once at operating temps, the misfire and chain slap returned along with another CEL for the same code.
Fairly certain I have tensioner issue. Have ordered all new tensioners, chain ramps and check valves and cover bolts (I can return what I don't actually need).
For those of you that are afraid to tackle this, it's almost as easy as changing your oil. I didn't even fully remove the intake when I changed sensors (I also didn't remove the covers) and it took me less than an hour start to finish. Once the tensioners and related parts arrive, I fully remove the intake to access the covers but that shouldn't add much more than 30 minutes to the entire process.
My big question here is does anyone have a copy of the timing set procedure if I need to do the chain because of stretch?
Thanks!
*WHOOPS! Wrong forum guys.*
Last edited by Ubercarfan; 12-09-2019 at 01:02 PM.
Reason: Wrong Forum
sound definitely not motor shaking, because of the frequency and metallic feature, it is the timing, I cannot imagine how the timing make this sound (maybe timing chain slapping the block wall due to excessive slag?)
It's definitely not because of the motor shaking. It's definitely a chain slap coming from the bank 1. I'm pretty certain the tensioner has failed and allows chain slack. I'll update once I pull it apart.
The part number for the cover bolts is: N 000 000 006 365
They are M6 X 16 with 16 total for both banks needed. I am a 276.952 engine.
Last edited by Ubercarfan; 12-09-2019 at 01:57 PM.
Reason: Engine No Included
thanks bro for the info. Don't be surprise if you open the cover up and find out a good chain tensioner. In my case, the slap remains with a new tensioner installed, this is still the puzzle to me .
01-24-2019, 10:40 PM
