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So i have a 2013 ML63 with the performance package and about 105k on the dash. I'm the second owner and to my knowledge it has never been tuned. I have babied it and never pushed her hard other than maybe some rips in a tunnel. Always changed the oil with Liquimolly on time.
As of recent ive been chasing a tapping/knocking noise that has me confused and worried at the same time. So the noise isn't the normal upper ticking sound that we get. This noise seems to be coming from the lower right side and can be heard better through the wheel well. Also the sound is only there when the engine is hot. Also the noise increases with acceleration. I have No CEL or misfires. I have clean oil and filter with no evidence of metal. Of course worst case scenario is rod knock but im inclined to believe it might be something else.
What could this noise come from? Exhaust manifold bolt? Bad spark plugs?
I'm trying to narrow it down before I spend the money and send it to the mechanic or try and dump it.
Last edited by Zerocarpileup; Jul 16, 2022 at 10:01 PM.
Just did a spark plug change and the noise is still there. Spark pugs looked pretty normal without signs of anything. Took a peak into the combustion chambers but my borescope isn't dual camera so i couldn't see the walls very well. ill be looking for an exhaust leak next.
i've got the same year ML63. When I start it cold in the morning the ticking noise is very distinct and loud, once engine warms the noise goes away. However, even when warm when you open hood noise is still there although not as loud as during cold start. I'm planning to change lifters and see if it takes care of it. If not, then your repair bill likely will be in high 0000's.
Problem with investigating these type of issues is that no one even MB dealers can pick up unless engine is stripped. But that's in itself costly. Better do lifters and then save $$$ or just sell the car if the noise doesn't go away.
I had a 2012 E550 with the M278. It had a little noise at cold start from the time I got it at 65k till I sold it 5 years later at 112k. Never had a problem, noise goes away after a few seconds running. I always warmed it up until the idle dropped on cold starts.
Hey, did you manage to change the lifters? Did it make any difference? I have had the same problem for a while now. Its worse when the weather is cold.
Kinda crazy that with so many M157 owners claiming to have the same exact noise, NO ONE has been able to figure this out. I look at so many post on so many different platforms that have been around for YEARS and still nothing. I hear chatter about bent conrods, dual mass flywheel and stuck lifters but still no one has reported performing an actual repair and lived to tell about it. Does anyone have any advice other than "take it to the dealer"?
Kinda crazy that with so many M157 owners claiming to have the same exact noise, NO ONE has been able to figure this out. I look at so many post on so many different platforms that have been around for YEARS and still nothing. I hear chatter about bent conrods, dual mass flywheel and stuck lifters but still no one has reported performing an actual repair and lived to tell about it. Does anyone have any advice other than "take it to the dealer"?
Did you live to tell?
I have the same noise and have read many tales about it on other M157/M278 but none reported a fix except one W212 owner who found a faulty/leaky spark plug. Others just replace the engine or get rid of the car which I'm sure will fix any engine issue but it takes out the fun of chasing and fixing the root cause.
Also, I've listened to some "normal" sounding engines and this noise rhythm is there in varying degrees but often not as loud which makes me think it's been amplified by exhaust leak or something. Oh well, I hope to live to tell!
I'm standing by my previous comment of "it's normal and not an issue" - at least on cold starts - but I came across some info before regarding replacement / update of the timing chain tensioner parts on earlier M278 / M157 engines. It may be in a TSB, I don't recall where I saw this, but I believe there are updated parts to go along with the updated chain, but much less invasive of a job, changed externally, if you can get to them. I think many people who consider themselves mechanically inclined, but have not experienced DI engines before are put off by the noises they make.
I'm standing by my previous comment of "it's normal and not an issue" - at least on cold starts - but I came across some info before regarding replacement / update of the timing chain tensioner parts on earlier M278 / M157 engines. It may be in a TSB, I don't recall where I saw this, but I believe there are updated parts to go along with the updated chain, but much less invasive of a job, changed externally, if you can get to them. I think many people who consider themselves mechanically inclined, but have not experienced DI engines before are put off by the noises they make.
Did your "normal issue" sound like @Zerocarpileup description in the OP and the audio/video example? This thread is not about the widely known cold startup rattle that can be resolved by installing new tensioner, check valve, chain, etc.
I'll also share more of my symptoms, observations, and troubleshooting steps most of which I've posted elsewhere in a quest for a root cause. I'm hoping this rekindles the topic and collaboration to search for a root cause.
I bought the car in this state with full knowledge of the noise and the potential worst case scenario of engine rebuild/replacement. I welcome all thoughts and input about the problem, but please let's keep things on topic (comments like replace the engine, these M278/157 engines are junk, engine is worth more than the car so forget it, get a new ride, etc. are off topic and not helpful).
Observations
Car runs fine otherwise. No malfunction/check engine light related to the problem.
Noise is on bank #1 (the right side ) and the noise is present all the time except at >2000 RPM at idle.
Noise gets slightly better when warmed up. I can barely hear it with windows up and at a stoplight when fully warmed up but it doesn't go away.
It's worse under load/acceleration. It's completely gone (can't hear anything) when my foot is off the gas pedal while coasting or braking
During gear shift under heavy acceleration, it seems to disappear momentarily during the shift transition
At cruising speed (60 - 100 mph) when acceleration is light, noise is mostly gone
Noise is most distinct at idle speed of 600 RPM. It's still present during a high idle (900 - 1000 RPM) on cold startup, but it seems to "settle in" with distinct taps when idle decreases to 600 RPM
Noise frequency increases with engine RPM
My noise frequency is at exactly 1/2 the engine RPM which seems to point to something on the upper end (see chart below)
The noise coincides with cylinder #2 firing event. This cylinder also has the highest values for engine smoothness (up to 2).
Compression is high on all cylinders (205 -230 psi). It's lowest on cylinder #2
When I lubricate all the coil boots with dielectric grease, cylinder #2 spark plug boot seems hard to take off even after a short engine runtime
I get white smoke from both tailpipes on cold startup which seems excessive and takes too long to clear up, but it does clear up when engine is fully warmed up
Stethoscope analysis shows noise is distinct on the top side near cylinder 1, 2, upper timing cover, but also loud on the bottom when listening at oil pan
I can hear the pulsating noise through the exhaust. Seems loudest in bank #1 tail pipe
Engine consumes oil but I believe I have a leak around the turbo/manifold but it may also be burning some oil. I can smell the oil burning. I consider this an unrelated problem to address at the appropriate time
Most of the cylinders on the right bank #1 have scoring (haven't inspected bank #2), but I think the scoring is a red herring. I believe the scoring is what makes most give up and replace/rebuild the engine or sell their car before getting to the bottom of this noise. I respect those decisions.
When I do work under the valve cover (rockers, camshaft, etc.) and button things, noise seems to disappear the first several seconds after the engine start (a bit subjective so not certain).
Monitored oil pressure and it's within factory spec with no odd behaviors (see chart below)
Mitigation Attempts so far that have made no change
Engine oil flush with Liqui Moly and fresh oil with genuine filter, no change
Remove oil filter and run engine to check. No change
Tried heavier weight oil 15W-40. No change
Replaced spark plugs, torqued to spec and ensured proper indexing
Replaced all rockers and lifters on bank #1. No change
Replaced camshaft and actuator on intake and exhaust on bank #1 with known good parts (my original didn't look worn or defective). No change.
Replaced upper chain tensioner on bank #1 with known good one. No change
Cylinder leak down test is over 94% on the cylinders including cylinder #2
Smoke test on the combustion chambers was fine including cylinder #2
In-cylinder/running compression test shows no obvious issues in the cylinder health including cylinder #2
Swapped fuel injectors and coils around with no change. I actually ended up replacing cylinder #2 injector because it failed.
Disabled combustion on cylinder #2 with no change
My other thoughts
I know my engine has other problems (scoring, oil leak/burning, etc.) which I'll address, but I believe they're unrelated
I believe the problem is from cylinder #2 based on observations noted above. The things I haven't ruled out are valve guides, exhaust leak, and bottom end damage.
If I listen carefully to clips of other M278/M157 engine running, I can hear this cadence of noise. It varies from subtle background noise dominated by the injectors ticking and normal engine noises, to the same noise that but not as loud as mine. Please take a good listen to your engine for slow subtle tap tap tap noise. Knowing what components causes this rhythm may give a clue
This could very well be something in the bottom end (rod, bearing) but not ready to pull the engine just for inspection. When I pull the engine it will be on the way to a rebuild to address the cylinder scoring
I'm attaching some annotated diagnostic info.
Blue trace is tapping noise. Red tall trace is cylinder #1 ignition event, lower red traces are other cylinders firing events in the firing order. Note that noise RPM is 1/2 of engine RPM
Cranking compression test shows no apparent defect in cylinders and valves
Oil pressure tracking showing proper response of the variable-flow oil pressure pump
Interested in how this plays out. I too have some odd issues coming from a m157 ml63. Here are my details:
2012 ML 63
127xxx miles
m157
new timing chain, new magnets, cam position sensors
new spark plugs
bone stock. no tune. NOT p30 performance pack
ISSUE:
Burns about 1qt of LiquiMoly 5w40 every 750 miles
black dust like residue appears on the rear hatch every fill up
OBSERVATIONS AND STUDIES:
compression 145-160psi on all 8 cylinders
the spark plugs looked used but not wet or burned up
small spots of external oil residue but no dripping and no signs of serious leak
engine runs perfectly
no codes ever
engine sounds strong, pulls like a nuclear power battle cruiser
Interested in how this plays out. I too have some odd issues coming from a m157 ml63. Here are my details:
2012 ML 63
127xxx miles
m157
new timing chain, new magnets, cam position sensors
new spark plugs
bone stock. no tune. NOT p30 performance pack
ISSUE:
Burns about 1qt of LiquiMoly 5w40 every 750 miles
black dust like residue appears on the rear hatch every fill up
OBSERVATIONS AND STUDIES:
compression 145-160psi on all 8 cylinders
the spark plugs looked used but not wet or burned up
small spots of external oil residue but no dripping and no signs of serious leak
engine runs perfectly
no codes ever
engine sounds strong, pulls like a nuclear power battle cruiser
Does your engine make noise similar to the one in the video clips above?
Your compression seems low but I guess it's OK if you have no codes/misfire and it's consistent across all cylinders. Did you measure with a dial gauge and on a hot or cold engine?
To me it seems like you have found your problem. 1/2 speed right before the #2 ignition event. I would guess the #2 intake tappet. Have you made a further determination?
By the way, how did you log your data? This is one of the more lucid diagnoses I have seen on this forum.
To me it seems like you have found your problem. 1/2 speed right before the #2 ignition event. I would guess the #2 intake tappet. Have you made a further determination?
That was my initial suspicion too, but see my mitigation attempt #5 where I replaced all 16 hydraulic tappets and rocker arms on bank 1 with no difference. I even replaced the intake camshaft (albeit with another used one) with no difference.
Recently I completed a 3000-mile trip within a week. This rig cruises smoothly at 70 - 100mph for hours with no issues at all other than the noise as described before. It did consume 2 quarts of oil in the process which I believe is a combination of leaks and burning due to scored cylinder walls. I'm beginning to suspect this noise may be caused by exhaust leak at the manifold but I can't explain why that happens only under load (even the slighted feathering of the gas pedal causes the noise) but seemingly disappears when foot is off the gas during coasting regardless of engine RPM. Does the M278 disable combustion during coasting? I've also heard suggestions that this may be caused by the dual-mass flywheel which kind of make sense with the noise disappearing during shift transitions but it doesn't explain the RPM and cylinder event correlation.
I'm actually thinking about taking this in to MB dealership and share all my diagnostics with them to see if they'll have other thoughts/insights. I'm just concerned that they may give me the usual runaround that "your cylinders are scored, you need a new engine" or "we've got to take the engine apart and go from there." The noise is so distinct that I'd think MB dealership mechanics or their field engineers can recognize what is causing it having ruled out potential causes from my diagnostics so far. More suggestions/thoughts from this forum is welcome.
Originally Posted by mbwillgrubs
By the way, how did you log your data? This is one of the more lucid diagnoses I have seen on this forum.
I log this data with oscilloscope and homemade pressure and pulse transducers.
Blue trace is tapping noise. Red tall trace is cylinder #1 ignition event, lower red traces are other cylinders firing events in the firing order. Note that noise RPM is 1/2 of engine RPM
Each cylinder in a four-stroke engine fires once every other revolution. Are you confident of the last sentence above?
Each cylinder in a four-stroke engine fires once every other revolution. Are you confident of the last sentence above?
Yes, quite basic and obvious knowledge and hence why cam revolution in 4-stroke engine is 1/2 crank RPM as I noted in my analysis. Any insights to share about potential source of the noise given all the above?
Sorry, missed the replacement of the valvetrain components. I know my M157 is a tap happy engine. I always attributed it to the injectors, high pressure and all. Like yours, engine pulls like a locomotive.
The half speed, right before #2 ignition just strikes me as significant. Could be an injector at that time as well but you had changed those as well.
Sorry I can't be of more help. I am still really impressed with your diagnostics.
Each cylinder in a four-stroke engine fires once every other revolution. Are you confident of the last sentence above?
then:
Originally Posted by tadiguy
Yes, quite basic and obvious knowledge and hence why cam revolution in 4-stroke engine is 1/2 crank RPM as I noted in my analysis. Any insights to share about potential source of the noise given all the above?
If you mean my confidence in my statement that "noise RPM is 1/2 engine RPM" then yes, I'm quite confident. As you can see from the blue noise spikes, the ruler measurement from spike-to-spike is 300.5 RPM. This was taken when the engine was idling around 600 RPM. Also, even before taking these scope measurements, I captured the audio of the noise and did a spectrum analysis of the audio which also confirmed the noise happens 300 times every minute over the background noise. I could also tell just by listening that it's a low RPM noise. I also did audio spectrum analysis of similar audio posted by others here including @Floridah and came to the same conclusion about noise count per minute. Do you see or interpret this differently?
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