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Does the noise go away as you rev the engine? To me the noise sounds like something internal to the block ie piston slap, rod knock, wrist pin etc.
or the VVT? Hope the VVT goes first before something more internal goes wrong. Fingers crossed.
I think the idea of recording with more fidelity at the top, and somehow lower on the driver side of the engine is worthwhile. Even a broomstick on the timing cover to isolate where the noise is coming from.
I think I opened my own can of worms by recording my engines. Well, better earlier than later. Now I need to start my parts list not to be stuck because I forgot something.
Yes would be more than happy to be wrong. I have a similar noise in my M272 that I am attributing to piston slap based on information from these boards. Wouldn't think that would be an issue with the M276.
What is the real evidence we are dealing with? A not-great recording? Inconclusive.
Are the other symptoms? Codes/CEL? Misfire, rough running, poor fuel economy or unburned fuel smell from the tailpipe?
Y’all are rushing to worst case conclusions.
You are correct that the original recording is not optimal.
Compared to the other two recordings of my engine indicates there is something off on the OP's engine noise. Unfortunately, @Arrie pointed out that my E350 also has a subtle additional noise (likely around the HPFP) not present in either of the two other recordings.
On my side, I do not think we know what is wrong, but something is OFF. Critical? not enough information. Worth pursuing the diagnostic? In my opinion: definitely, because these engines are NOT cheap to fix, and the earlier it is diagnosed the better.
Sure we need more data, perhaps reports from a scanner. I definitely do not have codes on either vehicle, but I can tell the ML's engine is butter smooth compared to the E which by no means has shown any sign of concern until this recording.
You are correct that the original recording is not optimal.
Compared to the other two recordings of my engine indicates there is something off on OP engine noise. Unfortunately, @Arrie pointed out that my E350 also has a subtle additional noise (likely around the HPFP) not present in either of the two other recordings.
On my side, I do not think we know what is wrong, but something is OFF. Critical? not enough information. Worth pursuing the diagnostic? In my opinion: definitely because these engines are cheap to fix, and the earlier is diagnosed the better.
Sure we need more data, perhaps reports from scanner. I definitely do not have codes on either vehicle, but I can tell the ML's engine is butter smooth compared to the E which by no means has shown any sign of concern until this recording.
XENTRY (search providers on this site) is the best-practice for this. Fuel, cam timing and ignition systems can all be thoroughly analyzed using live sensor data. Anything less is guessing.
XENTRY (search providers on this site) is the best-practice for this. Fuel, cam timing and ignition systems can all be thoroughly analyzed using live sensor data. Anything less is guessing.
I wouldn't even know what to look for I have access to a scanner but not the Mercedes specific scanner.
It is easy.
Get a suitable dummy load resistor and also use some sort of LED as visual.
I can dig up my files and tell you how many milliamps the switch is consuming, so that your DIY-Hack will not trigger any DTC at ECM
Look at your N3/10 wiring diagram, you probably have an X26 intermmediate connector too like my 3.0, hack it there and not at ECM connector
Thanks Surya for your mindshare.
I'll be happy to be the first one around here to pioneer that idea of a simple "oil pressure" enhancement.
I am nearly positive something so obvious must have been done already on a German cousin: VW, Audi, Cooper... I am a loyal Honda Motors fan without the vast exposure of a mechanic shop.
I swear if the burnt oil smell return, I will yank the solenoid connector from the engine front.
The oil vaporized on the pistons must leave residues in the 3rd oil-control ring bleed holes. Once plugged up oil has no place to go but up through the 2 pressure rings.
I am not yet clear why the pistons super-heat has stopped now. I sort of attribute that to the toc-toc of injectors working better spray timings (clip in later post). Pistons are not heated so much
-Or the damn ECU has a bug in that new solenoid logic just like the amazing ALT-Control yoyo bug.... you know essential feature turned into unnecessary chaos.
Given a chance to return oiling to normal, I'll take it.
Last edited by CaliBenzDriver; 08-09-2023 at 07:56 PM.
I swear if the burnt oil smell return, I will yank the solenoid connector from the engine front.
To be honest, I used to associate the burnt oil smell with the Italian tune-up along with the creaking sound of the exhaust once the car was in the garage. Similarly, the missing quart every 10K miles was associated with heavy driving; however, that one it is also gone. On the current oil, @3K, the level is at the mark. So far, my assumption is the consumption is non-linear, i.e. as the oil gets older/driven more is consumed.
I have not noticed the burnt smell for quite a while, likely since the summer of last year when Indy switched oils to 5W-40. Related? More sedated driving? My wife does not think so.
For comparison, I just went out and started both cars, they have been sitting for more than 12 hours, and the recording started after turning them ON, and enough time to open the hood and set the light. That is, below operating temperature, but already idling.
I do not hear the tap-tap, and I am not saying those two are perfect either.
JC, Your sound clips are ok for M276, sort of homogeneous even metalic freeplay but all right. Great detective filming around both engine banks 1-2.
Here is what my 50K engine idles like minus the startup rattle..:
-- the Rpm steps down by couple as the O2/Lambda are being warmed up.
-- At 2:01 there is that new-to-me clear transition from tic-tic to the toc-toc - Bosch ECU switches injection modes, right? My engine used to be only crickets both hot or cold only tic-tic since new.
-- After that the RATTLESNAKE sounds HPFP roling the 3 or 4 lobes on single V6 pump. (V8 2x HPFP)
So the tap-tap-tap i don't think is rattlesnake pump
1 of 3 chains slapping on guides or bank1 tensioner &c-valve?
+++++ there is a bit of tap-tap with same frequency but not so pronounced... It's there but smooth without the taping
My bet's on the amazing tensioner.
++++ weak valve lifter:
you know how engines always stop at the same positions? The valve springs and lifters get held in that state for prolonged times.
Yet the tap-tap is too slow to be a single cylinder issue.
+++++ "dead or alive" :
We need a bounty hunter to help locate the tap-tap...
Last edited by CaliBenzDriver; 08-09-2023 at 08:08 PM.
If the suspect is the HP fuel pump and/or its roller lifter, and your engine is therefore the M276 direct injection, here is how we can narrow it :
01. Do a proper video recording ( don't move don't shake ) closest to Bank 1 ( Right side ) firewall, where the fuel pump is at, hoping we can get a good audio.
If an M276 3.5 NA , its camshaft fuel lobe is 3 lobes. See below :
This means for say 600 idling RPM, divided by 2 ( because camshaft is 1/2 speed of crankshaft ) and then multiply by 3 fuel lobes.
So 600 / 2 x 3 = 900 pumping events at 600 RPM idling. This we can catch its audio peaks if you record well and we can then verify, are we hearing a 900 RPM or 15hz audio peak ?
If we are, we have narrow down to HP fuel pump and/or its roller lifter.
That is why the audio recording need to have that tok-tok-tok sound clear enough for the audio section of the video editor to show their magnitude.
Based on M276 3.0 Turbo, but HP fuel pump position and overall this 3.0 is so similar to 3.5
However, based on your short recording of the tok-tok-tok sound, your issue is not with HP pump region, the frequency is too low .
Here is why I said so :
If you really want to get the tok-tok-tok sound frequency right, do a full 30 seconds video and set your camera to do 60FPS, resolution 1080p is enough.
You need to do a slow swipe to see where the highest noise is as RECORDED, and when you find it, use that location to do a full 30 seconds video recording.
Practice till you get the loudest tok-tok-tok sound and share with us.
Make a paper sicker ( masking tape ) label on your engine as shown below, divide it into 4 zones so you can later ID where the sound was loudest, when and if that
big black engine cover-intake air combo plastic get removed.
When I said practice, practice as a videographer, so that we can see by position where the loudest sound was.
What you see we can not see, we can only see the video you took. Use wide angle first and then slowly close in for closer view.
When showing someone by photo or video, one need first to do wide angle and then zoom in on the item/location.
Have fun recording...................
Ok got home and used a stethoscope to do some listening. I went all over the engine with no sounds until I went on top of the driver side front coil pack. It is very loud and can actually feel the tap. What should my next steps be? Tear it down? Pull a plug and get an inspection camera?
Does the original video I posted with the knock sound like 600 rpm? Or slower? Could it be a valve rather than the piston stroke?
Sure, front driver's side is one of the easier cylinder to inspect. Pull the plug and post photos of it. Use an endoscope (cheap on Amazon) and post the photos. Look at the top of the piston and cylinder walls.
Sure, front driver's side is one of the easier cylinder to inspect.
Pull the plug and post photos of it. Use an endoscope (cheap on Amazon) and post the photos.
Look at the top of the piston and cylinder walls.
What do you think causes the pistons to score cylinders located right next to the oil pump (No1 + No4) ?
Piston overheated ?
Sure, front driver's side is one of the easier cylinder to inspect. Pull the plug and post photos of it. Use an endoscope (cheap on Amazon) and post the photos. Look at the top of the piston and cylinder walls.
@S-Prihadi would you mind sharing the endoscope you got, the one that can check forward, i.e. cylinders and piston top, and backwards to check valves and head chamber? You got one correct?
If it is definitely on Bank 2 front cylinder, it can be internal or at the top: injector, cam lobes rolling on top of the buckets. Let's say it is around the front cylinder, but maybe a bit forward. Then you have the exhaust VVT if you feel it is towards the outer side. With the engine OFF, check how difficult would be to place the stethoscope on the block side wall around the front cylinder, the more forward the better to avoid the neighbor cylinder (middle in the block). If you feel it is safe, and manageable, you can try then with the engine running. Please be careful not to get burned, or else.
NOTE: I avoided using cylinder 1 nomenclature since Bank 2 only has cylinders 4, 5, and 6 and someone else may get confused before reading the whole thread.
If you have/decide to open the timing covers, here is a video showing a failing VVT
What do you think causes the pistons to score cylinders located right next to the oil pump (No1 + No4) ?
Piston overheated ?
I don't think they're scored on OP's engine. The cause for the M278/M157 imo is cheaped-out engineering by MB in relation to cylinder coating alloy chemistry and thickness, or a manufacturing process problem in the cylinder coating step.
@S-Prihadi would you mind sharing the endoscope you got, the one that can check forward, i.e. cylinders and piston top, and backwards to check valves and head chamber? You got one correct?
If it is definitely on Bank 2 front cylinder, it can be internal or at the top: injector, cam lobes rolling on top of the buckets. Let's say it is around the front cylinder, but maybe a bit forward. Then you have the exhaust VVT if you feel it is towards the outer side. With the engine OFF, check how difficult would be to place the stethoscope on the block side wall around the front cylinder, the more forward the better to avoid the neighbor cylinder (middle in the block). If you feel it is safe, and manageable, you can try then with the engine running. Please be careful not to get burned, or else.
NOTE: I avoided using cylinder 1 nomenclature since Bank 2 only has cylinders 4, 5, and 6 and someone else may get confused before reading the whole thread.
If you have/decide to open the timing covers, here is a video showing a failing VVT
Juan, how about not opening the timing cover to just look .... instead use the stethoscope to listen for a caracteristic click This is cause of "Hello Rattle"
Rotate crank pulley while listening for a sharp VVT click on both bank 1+2.
Listen in the center between intake/exhaust VVT: a tick means a bad VVT needs a valve cover job, not just a tensioner.
In the video you picked for VVT test : observe how the tensioner shaft keep coming in and out. Super loose.
Last edited by CaliBenzDriver; 08-10-2023 at 01:15 AM.
@S-Prihadi would you mind sharing the endoscope you got, the one that can check forward, i.e. cylinders and piston top, and backwards to check valves and head chamber? You got one correct?
To have a complete good view, you will need 2 types of endoscope.
For valve opening, I use Teslong NTS500 dual camera one :
the side 90 degrees camera is the one able to see the valve opening or TDC.
This camera head can pop out so very little out of the spark plug hole, as such it can then see valve from close to open.
Like below :
This camera "push" cable is also stiff, so it can be used to see HVAC Evaporator and many many more things. You can push it into spaces without needing a guide because the "push" cable is stiff and can act
like a mini shaft.
===========================
This is the articulating one I bought, 8.5mm version Android. https://www.aliexpress.com/item/4000...21ef1802mCusre
Its "push" cable because it can articulate, is actually very soft in the sense it is not stiff and you can't really use it at location where the push cable does not get something
to slide against as a support surface. I hope my explanation make sense.
If used in drop down mode like seeing a cylinder, this is very good, gravity helps and its bending or articulating action need room, hence this one CAN NOT see valve opening event as
good as the Teslong 90 degrees camera because in order to articulate the "push" cable need to enter the cylinder about 2 inch /5 cm deep for it to be able to do the articulation.
So what I get is seeing the valve from underneath it and I get much better image quality too because I can deepen or shallow the "push" cable into cylinder as a way to get sharp focus.
Also being an 8.5mm OD, it has more led lights and a better camera too.
So I get this better resolution and brightness :
==========================
Seeing the piston.
TESLONG
The articulating unit
Those dumb-azz looking yellow-ish stain on the liner is the Nano Coating for M276 3.0 Turbo and AMG engines. Frequent short time engine start to move the car around my garage and short drive is harmful.
They are OK, albeit looking like shi-et , I post it here : https://mbworld.org/forums/e-class-w...bad-liner.html
Well I guess I should have done this sooner but thank you everyone for your input. I learned a lot and what I need to look out for in the future.
This morning I removed the front coil pack and started to pull the plug. It was not tight at all so I was leaking compression. Tightened the plug and no more knocking. This was my fault as I did the plugs about 45k miles ago. But that didn't even cross my mind as being the culprit.
Well I guess I should have done this sooner but thank you everyone for your input. I learned a lot and what I need to look out for in the future.
This morning I removed the front coil pack and started to pull the plug. It was not tight at all so I was leaking compression. Tightened the plug and no more knocking. This was my fault as I did the plugs about 45k miles ago. But that didn't even cross my mind as being the culprit.
Great you found the problem. I am sure you should feel extremely happy, I would.
By any chance, did you torque them before to specs? did you add any anti-seize back then?
Stay around if you want to continue learning about your vehicle in this forum. I met someone with a CLS550, and he mentioned he follows the W212 forum because it is extremely active and informative.
Great you found the problem. I am sure you should feel extremely happy, I would.
By any chance, did you torque them before to specs? did you add any anti-seize back then?
Stay around if you want to continue learning about your vehicle in this forum. I met someone with a CLS550, and he mentioned he follows the W212 forum because it is extremely active and informative.
I honestly can't remember. It was 3-4 years ago. I typically always do antiseize. But rarely TQ stuff.
Well I guess I should have done this sooner but thank you everyone for your input. I learned a lot and what I need to look out for in the future.
This morning I removed the front coil pack and started to pull the plug. It was not tight at all so I was leaking compression. Tightened the plug and no more knocking. This was my fault as I did the plugs about 45k miles ago. But that didn't even cross my mind as being the culprit.
Thanks for reporting your finding! Glad to hear it was minor.
Well I guess I should have done this sooner but thank you everyone for your input. I learned a lot and what I need to look out for in the future.
This morning I removed the front coil pack and started to pull the plug. It was not tight at all so I was leaking compression. Tightened the plug and no more knocking. This was my fault as I did the plugs about 45k miles ago. But that didn't even cross my mind as being the culprit.
Congrats. Good thing you didn’t replace the HPFP! Assume simple things first.
That is the part. Like I said, I replaced the pumps and these Roller Tappets. I had very similar noise as the cam shafts make but much louder with kind of rattling side to it. It was very annoying, and I did not want to drive the car like that and changed both pumps and Tappets and noise went away. I don't know if it was the pumps of the Tappets but both Tappets show worn point where the pump makes contact, and this could be the reason for the loud noise.
08-09-2023, 11:33 AM
