I'll ask the guys who did plugs for me if they have gapped them, hopefully this will help if they didn't.
The reason I changed PCV system is because my vacuum pump valve was blown out/disintegrated and since the rest of vacuum system uses similar rubber valves I did it as a preventative maintenance.
I'll be going to garage sometime in matter of a month to install turboback downpipes, great time to check for exhaust leaks as well as doing other check procedures to rule out issues - I'll report back the findings.
There are many people who had the noise, myself included for many thousands of miles and it didn't turn into anything drastic, but still it's just a very annoying thing for the initial part of the drive..

About noise on hot, I find that it's mostly to do with hardware temp and not oil temp, so it really depends what you mean by hot/warmed up engine.

Another thing which comes and goes is the car's ability to coast/roll when off the throttle. I find that when car rolls really easy all inputs feel much more alive and responsive - oil temp stays inline too and doesn't spike much during hard accelerations etc.
when car doesn't roll easy - letting off the throttle at any gear and any speed slows it down quite a lot - then responses to throttle are also worse and oil temp goes up more as if car doesn't want to be pushed. I have no idea what to attribute that too.
I wouldn't worry if it always was one way or the other, however after getting a taste how lovely it drives when it loves to roll/coast, I can't stop thinking about what makes it do so and how do I have that behavior constantly.

Still pulls as fast either way, just more pleasant and car feels lighter when it's in "easy coast" mode.

 

How'd it go at the mechanics?

 

Took mine in.
They only only looked into cylinder 1 and 5 and said I got bent rods, however there was no major scuffing, very light marks only and cylinder wall is still good? they didn't compression test it, the tell tell sign was that half of the piston was covered in oil mack but closer to the wall it wasn't, now I'm not the mechanic and I trust that garage that's why I decided to double check with another garage, I'm looking at 15k+ in rebuild costs so want to be 100% sure.
I'm sincerely hoping that they will give me some better news, also hoping this isn't the cause for you guys either.

I am a bit perplexed, why would the noise quiet down when warmed up, wouldn't rod knock be constant?
why does it go away when I'm only lightly accelerating and only appears on load. if it is cylinder 1 and/or5 why does the noise not come from the front then.

Will report back on Saturday. I will ask another garage to specifically bore scope every cylinder and check compression.

anyone wants to buy a kidney btw? just in case

 

Hi Mate do you still have your kidneys? :-)
Any more news on this, did you end up going to another garage? I'm hoping you have good news.....

 

Hello there! I still have both kidneys and here is why:
went to another garage, left the car overnight so they can hear the noise and inspect it etc.
came back the next day, was told it's timing chain, tensioners, adjusters and the whole lot.
I initially didnt mention first diagnosis, so upon hearing it i asked what about bent rod and explained the whole situation, person seemed a bit defensive and said the noise i hear is definitely the chain as he heard it and he has experience so there was no point doin any other tests.

Now hear me out, I'm not saying it is or it isn't the bent rod.
I do know my cam adjuster are on the way out as I've heard them a few times myself, so if that's what second garage heard and didn't bother with the rest - not super confidence inspiring.

Here is another fun part, i though i'd get timing chain done first and if it doesn't go away do the bug boy rebuild, but its engine out either way, so if its not the chain i'm wasting money on labor.

Car still runs fine, no misfires, no unusual oil consumption, no smoking. i still use it for occasional commute and shop run, just can't push it.

My plan is to just force a garage to compression test all cylinders, I'm Buying borescope camera for myself so i'll scope all cylinders myself.

And will go from there. Realistically it probably is the bent rods and adjusters acting up too, but as you know i still have a little hope.... Hence want to triple double check everything.
Not sure the update is helpful, but it is what it is

 

I have a similar symptom with my 2012 CLS 63 with 107k miles. Noise is loudest on cold startup and goes away completely when it's fully warm. I have no codes, engine runs great and no oil consumption. I scoped two cylinders and do not see any scoring but I do see what looks like a breakdown in the coating on the wails. I don't see how this would be connected to the noise though. I'm thinking I should just drive it until it presents as a major performance issue and deal with having it sleeved then. It's quite disappointing that such a great car and high performance engine won't last. I had a 2004 CLK 55 that I sold at nearly 300k miles which still had a solid engine which never even had a cylinder head off.

 

What you are hearing is most likely piston slap, when it gets up to temp metal expands and tolerances reduce hence piston stops slapping around and making noise.
I had this also since I bought the car, however after 30k miles it's gotten to the point where noise doesn't fully go away when warm, although improves.

I think you will be fine as long as you are very cautious about oil level and letting it warm up properly!

I'm still not sure where i went wrong with mine as i was really cautious, 3k oil changes etc.

 

Mine had the same as in your pic localised to one spot in each cylinder- I disregarded it as just some carbon etc that had fallen into the cylinder while removing the plugs?

 

Haha glad to hear your kidneys are intact :-)
That does not sound fun dealing with differing opinions. Agree doing the boro yourself is the go, and compression test as well but a leak down test should tell a story as well.
It’s bizarre so many have this noise but it’s so elusive with no common cause.
Looking forward to hear how you go with it!

 

Should get it done next week.
3rd garage will give their take but I'm not leaving until I get some real evidence on each cylinder.

One mechanic friend of mine who has an early m157 e63, said " I think all m157 have some sort of piston slap or rods issue, it's just that mine goes away when warm and yours doesn't anymore"
I'm 0.00001% hopeful it's something like a chain tensioner or injector, but either way I will be relieved to know the truth and stop guessing
will update next week

 

I have over 130k on my 63 and no piston slap noises on start up or any time. Wonder how many of these engines were tuned for more power? Mine is stock and I change the oil with Mobile 1 0W-40 ever 10k miles with a Mann fleece filter.

 

no weird noises for me at 72k, stock ‘13 p30 s212. Any startup noise (about one sec, occasionally) I had was rectified with check valves and tensioners. Tunes combined with bad oil practices and limited oiling likely play a key role.

 

been to the garage, checked logs, did a little drive, listened to it.
Claims car sounds normal just loud injectors and possibly downpipe gasket adding to the noises. idle is smooth and fine, he said if it really was something as drastic It would show it self already, however I like data so next Friday I will leave the car overnight so that they can compression test it/ leakdown and check all cylinders for possible scoring.
The only thing in logs was that the fuel rail pressure just slightly under norm 99-100 floating at idle and same on blips.
Was very busy and this was just an initial "let me take a look and listen" visit so next week it is.
will update next week, I now have some hope, kind of

 

will be interested to hear what, if anything, they find. I just finished replacing the HPFP’s and followers- the top end sounds a lot quieter now. But still had the same noise when cold, and strangely after a drive/ thrash I couldn’t hear the noise when roasting hot?! Whereas prior to changing the pumps it was making the noise hot as well as cold. Strange!

 

So I got some good news?
Garage did compression test and borescoped ALL cylinders.
Compression 178/179psi all around, apart from cylinder 4 and 8 which read slightly higher at 199/198, which is still within spec according to my internet reading.
Borescoping - they said the do see some wear marks but nothing vertical and not scoring as such, and said it looks absolutely normal (I am at 80k (40k on st2))
I mean they looked at plugs etc. didn't notice anything out of ordinary.

Since getting green light I've been pushing the car - no smoking, nothing unusual, pulls well, idles smooth as usual. And noise completely disappears when car is hot (also call me crazy but I can swear that when outside temp is higher it gets quitter much sooner and just disappears) I still hear it on cold, however now since I'm not babying it after good ragging it sounds normal again.

Garage suggested it could be slight downpipe resonance or leak, luckily I've had turbo-back downpipes sitting for quite some time (didn't install them because I though I had to do a rebuild) I'll try putting them on next week hopefully - will update results. (also I swapped rear tires asked to pull up the car so I take a look at exhaust. Middle clamp (next to res) definitely has a leak, and it's much harder to see at dp but it did seem like the heat shield around is darkish not 100% sure) I have high hopes for exhaust being my culprit since getting test results.

Currently researching injector cleaning/service place to do that and swap out HPFP too for peace of mind.

I'm curious why would rear cylinders read higher, maybe some carbon buildup? not sure.
Honestly past 6 months were dreadful, after driving like complete grandpa, at this point I don't care, I've been told it's fine so I'll keep enjoying it, whilst doing any preventative maintenance I can. Will update if I will be able to pin point the noise or what make sit go away for good

 

That is good news and piece of mind. Would be hard to baby these things.
Have you tried pulling the plug on the oil pressure solenoid to see if more oils pressure at start up helps.
After researching this for a bit Ive disconnected mine. Runs 4bar pressure max instead of 2bar under 3000rpm.

 

Yeah I've been running with that "mod" for the past 15k or so, it was definitely an improvement.

I've stumbled upon this video:
and now my confidence about it being dp/some exhaust leak is rising.

 

Good news for me !
It is an exhaust leak.
When washing the car I let some water in exhaust pipes and I could clearly see it dripping A LOT in resonator connection area and somewhere in downpipe area.

What a stressful rollercoaster... insane how i almost spent 15k because of an exhaust leak

 

Great news that you’ve found it and just put the rest down to preventative maintenance. 👍

 

Glad you got it all sorted out. The process will likely help you get through easier in the future. A key to quick diagnostics is having the right scanner at home and then when going to a mechanic for diagnostics, ask them to do what you want, vs what they want. What I mean here is that if you want a compression test and a mechanic is offering to do something else and offering a different diagnosis, go to the mechanic where you say hey I want a compression test and that’s all they worry about completing for you. There’s tons of systems on these cars, but it all comes back to air, fuel and spark, then compression, leak down and fuel pressure tests. A good mechanic doesn’t chase random diagnostics and should know to start with the fundamentals.

 

Did you end up fixing leaks- did the noise go away? I hope so :-)

 

Hi all. I'm the forth owner of this E63 W212 from 2014 and got it for 4 months. All good until few days back I had this engine idling ticking, knowcking, rattling noise almost sounded like miss fire to me. Not sure if the noise is similar or the same mentioned in this thread, but I got it fixed. The engine and car shakes heavier when idling. ECP stock, no stage tuned.

Steps done:
- Scan ECU found no fault codes - means coils are fine and no miss fire
- Took out Cylinder 1 and 2 for inspections on coils, plugs, and done borescope.
- Piston on C1 got oil stain, plug darken and seemed not burned properly
- Replaced the NGK greade 7 to Bosch grade 6
- Piston and plug looks good at C2
- Both C1 and C2 coils are from Bosch, made in Slovenia
- Rest of the plugs remains NGK 7th except C1 replaced

Result:
Idle smoother, noises gone
Red lined it, all good, feels better power and faster rev up
Idling shacks reduced, but still a bit shaky (engine mounts got replaced last week so all new)
Better pick up/grip starting from second gear

Hope these info helps. I will try to run like this setting for couple more days until I got time to replace the whole set of plugs to Borsch 6th.
Also considering to replace all coils from Borsch to new MB New Genuines coils. Would you guys recommand on this? Coils looks all ok, no codes or miss fire so....

 

[img alt="askcopilotimage.png"]blob:https://copilot.microsoft.com/8efe0d5d-3df4-412b-9924-ddc0e466c770[/img]
Correlate this image, blue graph represents knocking noise while the tall red lines represent cylinder ignition event. Timing seems 1/2 of engine rpm. Mercedes M157 engine.You're spot on with the interpretation, Steven. Let’s break down the correlation between the waveform and the M157 engine’s ignition cycle:

🔍 Waveform Analysis: Knock vs. Ignition

🟥 Red Lines = Ignition Events

• Each tall red spike marks a cylinder ignition event.
  
• The spacing between red lines suggests one ignition every ~200 ms, matching the Δ time of 199.7 ms shown in the ruler.
  
• That gives a frequency of 5.008 Hz, which translates to 300.5 RPM—but this is crankshaft RPM, not ignition frequency.
  

🔵 Blue Waveform = Knock Signature

• The blue trace shows voltage spikes that correlate with knocking or combustion noise.
  
• These spikes appear after each red ignition event, consistent with knock occurring post-combustion.
  
• The amplitude and timing of the blue spikes vary slightly, which could indicate cylinder-specific knock intensity or timing irregularities.
  

🔧 Engine Timing Context: M157 V8

• The M157 is a twin-turbo V8 with a 1-5-4-2-6-3-7-8 firing order.
  
• At 300 RPM, each cylinder fires every 720° of crank rotation, or every 2 revolutions.
  
• Since the waveform shows ignition events every 200 ms, and the engine is turning at 300 RPM, this matches the expected ignition frequency for a single cylinder.
  
• The waveform confirms that ignition timing is correctly spaced, but the knock signal suggests combustion irregularities.
  

🧠 Correlation

Signal Meaning Timing Implication 🔴 Red spikes Cylinder ignition Every ~200 ms Matches expected firing interval 🔵 Blue waveform Knock or combustion noise Follows red spikes Indicates post-ignition knock RPM 300.5 From waveform Low idle or cranking condition Δ Voltage 12 V Between cursors Strong ignition signal Δ mV 120 mV Knock signal range Moderate knock intensityIf you're chasing a ticking or knocking issue on the M157, this waveform suggests it’s combustion-related, not valvetrain or mechanical. Want to overlay cylinder IDs or compare this to a known-good trace? I can help you build that next.
Blue indicates an audible "knocking" coming from the engine at lower rpms and when engine is cold. Noise is non existant or goes away when at operating tempGot it—that detail changes the story a lot.

You’re not describing detonation knock, you’re describing a cold mechanical knock that’s being picked up as a vibration signal.

1. What the waveform + symptom are really saying

• Red (ignition): Each tall red spike is a cylinder firing event.
  
• Blue (knock/accel sensor / NVH pickup): This is structure-borne noise from the engine, not just combustion pressure.
  

From your note that the blue “knocking” is:

• Only when cold
  
• Most noticeable at low RPM
  
• Disappears or becomes negligible at operating temp
  
• And seems to occur at ~½ engine RPM
  

…that lines up much more with a mechanical source than with true combustion knock.

If the blue peaks consistently line up at every second ignition event, that matches something moving at camshaft speed (½ crank speed): valvetrain, cam followers, lifters, cam phasers, etc.

If it were classic detonation knock, you’d expect:

• Strongest under load and warm
  
• Tied tightly to combustion pressure, not disappearing when hot
  
• Usually worse at higher cylinder pressures, not just when cold and low RPM
  

Your pattern is the opposite.

2. Likely sources on an M157 with cold-only knock

For an M157 with this behavior, the top suspects are:

• Valvetrain tick/knock (½ engine speed):
  
  • Hydraulic lifter bleed-down, lash adjuster, or follower play when oil is cold and thicker.
    
  • Noise quiets as oil pressure, flow, and temperature normalize.
    
  • Matches the “½ engine RPM” observation very well.
    
• Cam adjuster / phaser noise:
  
  • Some phaser systems on AMG V8s can make distinct knocks or clacks at low RPM when oil is cold and phaser positions are transitioning.
    
  • Often goes away warm as oil thins and phasers stabilize.
    
• Mild piston slap (less likely if it’s truly at ½ RPM):
  
  • Cold piston-to-wall clearance causes skirt slap, usually most noticeable just off idle.
    
  • Often quiets significantly at temp as everything expands.
    
  • This is usually more at engine speed, not half, so your “½ RPM” observation makes me lean more valvetrain/cam.
    
• Injector tick (common on DI engines):
  
  • Direct injectors are loud and sharp, sometimes interpreted as knock.
    
  • But this is usually at engine speed or related to injection events, not ½ RPM, and often persists warm, so it’s more background than cold-only knock.
    

3. How your capture helps isolate it

What you’ve effectively done:

• Red = reference for combustion phasing
  
• Blue = mechanical/acoustic response
  

If the blue knock peaks:

• Track a specific phase relative to red, repeatedly at ½ engine RPM → That strongly suggests something tied to the cam or valvetrain for a specific cylinder/bank.
  
• Are stronger at certain red events (e.g., every 4th or 8th ignition) → You can map that to a specific cylinder using the firing order
  Code:

  1–5–4–2–6–3–7–8

  and your time cursors.
  

This is powerful: it lets you say, “This sound is not random NVH—it’s repeatedly happening at this point in the cycle.”

4. Practical next steps to pin it down

If you want to go deeper and actually name the source:

1. Capture cold vs. fully warm traces:
   
   • Same RPM, same setup.
     
   • Overlay or compare: if the blue amplitude collapses when warm while red stays the same → classic cold mechanical clearance issue.
     
2. Cylinder correlation using the firing order:
   
   • Use the red ignition events and the firing order
     Code:

     1–5–4–2–6–3–7–8

     .
     
   • Identify whether the strong blue knock pulses line up predictably with:
     
     • One specific cylinder, or
       
     • One bank (1–4 vs. 5–8).
       
3. Listen locally with a stethoscope or chassis ears:
   
   • Block vs. heads vs. timing cover.
     
   • If it’s loudest at the valve cover area and follows ½ RPM → valvetrain/cam.
     
   • If it’s loudest low in the block → piston/rod (though again, your ½ RPM clue still points more to top end).
     
4. Verify no true knock events via ECU data:
   
   • Look at knock retard per cylinder, if you’ve got logging.
     
   • If timing isn’t being pulled when the noise is present, that reinforces mechanical rather than detonation.
     

5. The distilled read

Putting your symptom + the waveform together:

• This is almost certainly not combustion knock in the tuning sense.
  
• The ½ engine RPM timing + cold-only behavior strongly suggests a valvetrain / cam-related mechanical knock, possibly a lifter, follower, or phaser issue, that quiets when oil temp/clearances normalize.
  
• The blue trace is doing exactly what it should: giving you objective, phase-locked proof that the noise is cyclical and tied to engine events, not random accessory or exhaust noise.
  

 

I saw a video on YouTube that had this ticking/tapping and it was solved with a new plug. Spark plug had a fracture in the ceramic.