AlVoj

Hi there,

I recently purchased my MB but it has a ticking/knocking sound coming from the engine on the right bank. It is always there not just on start up. There are no other symptoms. Car drives fine no misfires etc. Timing marks are all correct also.

My car is a 2011 S500 with the 4.7 bi turbo engine M278.

So far I have done the following:
- intake cam adjuster
- check valve and chain tensioner
- replaced the lifters and rockers
- oil changes etc

I did notice that when replacing the lifters, there was a gap between the rockers and camshaft. Then on re-install, there was a gap again only on one of the rockers now.
I have seen that it mentions to check the oil supply to the top of the engine. How do I check this?

Any other thoughts or what I can try next? Any ways to rule out other items ideally without replacing parts unless necessary?
Someone has mentioned rod bearings is there any way to check if this could be an issue without pulling apart?

Any help would be much appreciated. I have attached photos of what we have done if anyone can tell if there is a problem with my camshaft etc and video of the sound?

I am not a mechanic, just do the research and work on it with my old man. I have taken to a few mechanics and the dealer but they have not been any help so far basically charging me to then say not sure and will need to pull apart.





Thank you

tadiguy

Did you ever figure out the cause of the problem?

AlVoj

Unfortunately not. I ended up replacing the engine.

I have the old one sitting there just haven’t had the chance to pull apart to see what the issue was.

I will update the forums if I ever get around to it though.

good luck if you have anything similar

tadiguy

Thanks for replying. Sorry to hear you had to replace the engine; these engines aren't cheap. Did you get a rebuilt engine or just pulled from another car?
I'm in the same situation with the exact same noise on the right bank (same engine in my GL550). Like you, I research and do the work I can and actually went through the same path as you before seeing your post (new lifter/rockers, oil flush and change, timing check, etc.). I have scoring in the cylinders but I don't believe that's the problem since both static and running compression + leak down tests are fine. I think there is a quick rush to consider the engine doomed with any sign of scouring.

My troubleshooting so far points to valvetrain problem rather than something in the bottom like a rod bearing. I pinpointed the ticking/knocking noise source as coming from cylinder #2 and confirmed there is a gap between one of the exhaust rocker arms and the cam lobe in cyl2 even with a new rocker and lifter. Rocking the rocker produces very similar knocking noise to what I hear when running. There is no sign of sticking valve or broken spring. So, I suspect the tip of the valve stem is worn or the cam lobe is worn/shifted. I'll be replacing the camshaft next since it's relatively easier to get to. If I end up having to rebuild the head or the engine, I'll have one new camshaft and a new set of rocker arms/lifters on hand already.

chassis

High pressure fuel pump? It’s on the right bank.

tadiguy

Negative. Noise is coming from cylinder #2 as I stated. I had to remove the high-pressure fuel pump to pull the camshafts on Bank 1 and didn't find any problem with it.

red996

What's your mileage? What year is your GL? Thanks!

chassis

Why did you do all of the work on the engine to begin with? What is your ownership history with this vehicle?

MBNUT1

You are obviously more knowledgeable and experienced with engines than I but wanted to share that scoring has been attributed to hot engine idle knocking on M272 and M273. I don't think that means the engines are doomed as they run fine other than the knocking noise at idle when hot.

tadiguy

Thanks for sharing that info. I’m sure scoring could cause noise under certain conditions, piston slap being one. I just think by the time it gets that far there will other issues like loss of compression or cylinder leak. Like the OP, my knocking starts right away on startup whether cold or warm and increases under load. The frequency is 1/2 the RPM so it points to something driven by the cams.

JohnLane

Your engine is equipped with hydraulic valve lash adjusters that are designed to run at zero lash.

If you are seeing lash on that valve the lash adjuster is not pumping up, or is not getting sufficient oil pressure to pump it up. Look for scoring in the rabbit hole the HLA lives in or a lash adjuster that you can compress with fingers.

The shape of the base circle on the camshaft is designed to keep the HLA from holding the valve open. Has been like this with hydraulic lash adjusters since the dawn of time.

tadiguy

Good info. I'm going to go down the rabbit hole to investigate oil delivery problems. The lifter is new and doesn't compress under finger pressure.

I know that much. I compared the lash on the two exhaust valves on the same cylinder with the camshaft base lobe circle at the same rotation. I expected them to both have the same amount of lash but one clearly has much larger clearance than the other. I agree the lifter isn't pushing up or (my other theory) the lobe itself is worn out or rotated. I run into a rotated tone ring once on an M278 camshaft with delayed start that I fixed for a friend so I could imagine these lobes also shifting. From what I understand, the lobes are pressed onto the shaft and it's not machined as a single piece.

JohnLane

Roller followers make for effectively zero wear on cam lobes unless one has been especially neglectful about quality of oil and changing it. If a cam lobe is having an issue you won’t be able to miss it. (Have you seen a flat lobe in one of those Chrysler Hemi things? Think along those lines. It will be mostly missing with a roller follower that doesn’t roll.). Cam lobes rotating on the cam? That will make a drivability issue AKA misfire code vs a noise complaint as valve lash will still be handled by the HLA.

Check that the HLA isn’t fully extended. If fully extended this implies the valve is not at the correct height. Hmmmm

tadiguy

I took both HLA's out to measure and one is 40 mils shorter so I'd say it's not fully extended. The rabbit hole looks fine; no scoring or any obvious abnormality. The oil delivery port in the head looks clear and when I shoot cleaner through it, it shows up in the other "good" ports. If there is coking or other blockage in oil delivery, I wonder where that would be. If it's low oil pressure I can't imagine why it will affect only one cylinder and lifter.
The thought about valve stem not being at the right height crossed my mind but nothing obvious from eyeballing it. The spring looks intact. If there is carbon build-up on the valve seat preventing full seating of the valve, I'd have expected that to show up in compression and leak down test, but those tests check out OK. I feel I'm getting close to finding the root cause. New/more ideas welcome.

BTW: When I first replaced the lifters in that cylinder, the knocking stopped (or greatly reduced) on startup. I couldn't believe my ears and thought it's been muffled by the noise from the high RPM and auxiliary air pump associated with a cold startup. I kept listening carefully and then about a minute later it started the characteristic knocking again. I didn't think much of it then, but in hindsight I suspect the lifter was fine on that startup and the knocking stopped because it was prefilled with oil was at the right height before installation until all the oil squeezed out and didn't fill up again.

JohnLane

it may be worth trying a different weight of oil to see how the HLA responds. Or just fit another HLA and see if problem is solved.

tadiguy

I've already tried different oil weight without a change. I'll try some Liqui Moly additives next.

I've replaced all HLA and rockers on bank 1 since I had the parts already for a planned rebuild at a later time. I also found two lifters that I could slightly compress with my fingers. The new HLA/rockers made no difference in the knocking noise.

The loud knock coincides with ignition events on cylinder #2 and it's at exactly one-half the engine RPM which made me think it's something driven by the cams. I don't hear the noise during extended cranking. Can this really be something in the bottom end like rod knock? If it's piston related, I'd have expected it to happen on every stroke of the cylinder which causes the noise within a revolution (e.g. every compression/exhaust stroke or every intake/power stroke). What could be theory or significance if for instance the noise is happening only on cylinder power strokes and not on exhaust strokes?

BOTUS

additives into modern manu spec oils are dangerous and should NEVER go in there

modern cars moved to quite different engine oils quite some time ago - look up low SAPS - the two ideas don't mix - old world additives will cause damage - you won't believe me - but they re engineered materials and design to work with low SAPS changes - the old stuff is not suitable - people need to remember slick 50 and its ilk was for cast iron liners and manu practices years ago

these additives are 25 to 40 year old ideas that were vastly superseded in most car oils 10 years back and certainly aren't in anything designed in last few years

BOTUS

has this thing been tuned up ? most merc's bend a rod, the noises are odd a bit like the one you describe - many merc indies that have done lots of repairs and will recognise the noise having mostly spent the last 5 years bodging up wrecked AMG engines - its now very common (especially where the added boost is used well before 30mins engine warm up was completed) the bodge up is a cast iron liner on the offending pot and move the car on to the next mug.... $8k vs $40k repair (then add on the cost of removing the nasty map)

stick a borescope down the plug hole and look for cyl damage ?

tadiguy

See my OP for cylinder borescoping. No evidence of tune (project car is new to me). I know the idea of additives to anything sounds off putting but like modern cars, additives have come a long way. Low SAP is mainly geared towards preventing clogging DPF, DOC, SCR in diesel engines. Check out Molybdenum Disulfide friction modifies and other modern additives for gassers. These are the same additives that OE-spec oil blends boast of even in lower ppm. OE oil spec these days serve two purposes: (1) OEM pre-approval/licensing program which is essentially pay-to-play if you want your oil listed as approved by a major auto manufacturer and (2) improve fuel efficiency to raise CAFE sometimes at the expense of engine wear protection past the warranty years. And of course there is the overarching requirement to reduce pollution which is a good thing. There are few actual ingredients in the OE-spec oil that makes a difference in performance, like limit on ZDDP to prolong cat converter life past the federally mandated warranty period or HTHS viscosity specs. Nothing against OE-spec oil (I use them) but I believe a suitably classified API/ACEA oil won't perform any worse and the right additives do offer benefits to many modern engines.

BTW: I plan to rebuild the engine in the near future (steel sleeves and custom coated pistons) to address the cylinder/piston wear that most M278/M157 engines are destined to experience due to the Silitec or NanoSlide coating.

BOTUS

if current Merc and BMWs don't run the oil in the book somehow they run funny - I'm not on the engineering team trying to make they break.... but ford have sorted there's if you run the wrong oil the cam belt that runs inside the engine self destructs - they are all up to mischief - I can image the coating on the cylinders magically plays up on purpose

I was reading about low SAPS last year - totally different set up and the additives in bottle of stuff destroy the additives they now put in modern oils - these are now needed to suit the re engineering they did - I get they are lying that its all about looking after emission systems - in my mind its a nice idea they invented - use old oils the engine plays up, don't change modern oils at 2 the year mark and the modern additives self destruct and the car is bin material.... win win

last AMG I looked at the crank looked OK, the rod was nicely bent 2mm curve over its length, and its this that seems to make the light knocking noise, piston was toast - but the bore didn't look too bad - but they said it was trashed and was the third in 3 months they'd seen and were now used to stripping down to the block to have one cast iron liner fitted

BOTUS

timely post by someone else on Merc oils...

Anyway a while after purchase I replaced it with 229.51, after about 5k miles of use with what ever the previous owner put in.

A further 15k miles and I have replaced with 229.52 (from MB Newcastle). The engine is quieter and markedly smoother. I can still tell when it's ticking over, but it is much nicer than was.

The 229.52 is supposed to give 0.7% better economy, In the real world I can't imagine anyone would notice that. Otherwise though I'm not aware of a great difference in quality, but it feels like it.

AlVoj

Thank you, I ended up getting one from a pulled engine. I'm in Australia and parts for these are hard to come by compared to the US. I wanted to replace the head cover and camshafts as it was easy enough as I know I have a gap, but I ended up just cutting my losses and getting the engine instead. Only other thing I thought that it could be is stretched chains but if you have pinpointed to Cyl 2 then this wont be the problem for you.
I was hoping to sell the engine complete but looks like I will have to part out so I will eventually update the forums but could be a while as not in a rush to do it and to find the time.

BOTUS

I didn't think this one was your issue...

but the idea of cam follower wear / noise is common on a lots of stuff these days... mine has it... on the back of this point re 229.52 rather than 229.51,
as I needed an oil change I put the later type of oil in at the weekend and the cam follower tapping stopped instantly