I would say that part of the cam follower/lifter problem is lack of lubrication along with the softer metal of the cam lobes versus the follower buckets. We have seen M156 motors with north of 180K miles that tick like crazy but still run fine and when the revs pick up you cant hear it anyway.
Long term effects would be that eventually the lobes become so worn that valve lift is reduced to the point of it affecting the combustion process, causing reduced performance/driveability and increasing hydrocarbons because of an inefficient mixture burn affecting the O2 sensors and tripping the MIL lamp. The other issue is the cam adjuster failure which will affect timing and and also throw a code because timing can be altered.

replaced cam adjusters didn't notice any difference...

had Mercedes tech listen to it he said its ost likely the main bearing... and that for a 2006 its normal first year production bs and I shouldn't worry about it...
but I find that a bit suspicious... a main bearing making noise that I shouldn't worry about

Hey raverx3m,

Did you ever get this figured out? I have pretty much the same sound on my son's E280 (3.0L M272 engine). I replaced all the cam followers since that's what a mechanic told me it was, but it didn't fix the problem (although a few of them were not in great shape). I'm thinking connecting rod bearings, but I won't be sure until the engine is out. I'm leaning towards finding a wreck and replacing the engine.

Here's a video of my engine:

Thanks,
Miles

Hi Miles,

My engine was burning oil because one of the cylinders had scoring in the cylinder wall. I decided to replace the lower block for a another used one. In the process I found two valve followers with a problem and replaced them. One had a squared roller and the other was missing the spring that holds it to the tappet. The noise is less now but not completely gone. I will keep driving it the way it is now.
While in there I checked for play on the rod bearings and did not find a problem there.
Hope this helps.

Regards Frank

My guess is that one/some of the hydraulic tappets are not performing as they should.
You can try oil additives to fix it (like I will do tomorrow) and if that doesn't work you can replace on/some hydraulic tappets.....or just leave it like it is.....it's just annoying...
I cannot find any documentation on how to replace the tappets on a M272....on some engines it's simple and you only need a simple special tool....on others you have to remove the camshafts.
BTW: I checked the timing chain and balance shaft yesterday and the are in great shape.....my SLK350 has 270K km on the clock and is running fine...only a light tick on driver side near firewall....I can live with that if it is too much hassle....but I want the old girl perfect!

Any thoughts on replacing the oil pump to address this? I have the same noise in an '11 E350 and I've seen multiple reports of people trying to replace the followers with no luck. I did see one comment in the video below saying he had remedied this issue in a number of cars by replacing the oil pump. Suffice to say it's a huge undertaking so I'm reluctant to try that based on one comment, but would gladly do so if that's the fix. The only other "fix" is to add an oil additive to thicken up the oil, but I would rather fix the actual issue.

I do need to scope my pistons to see how the walls look. I would think if it were a rod bearing it would knock more when you rev the engine, but it pretty much disappears with the slightest of revs.

I own 3 m272 engines. 178k, 82k, and 78k miles. The 178k and 82k motors sound like yours, I think it's normal. I haven't checked the 78k motor. These aren't quiet engines. My e55 and ML63 engines make plenty of noise at idle too.

+1

I think it sounds fine...

One of the videos [from another member] it clearly sounded like lifter tick. I haven't run into that issue on these motors, but on some inline 6 BMWs the lifters should get "sticky"/gum up and not fully expand with oil pressure. Usually due to some combination or using dino or long drain intervals, short trips, anything that caused excess deposits and varnish... Usually running a good synthetic like M1 0W-40 for a few short drains intervals (like 1000 miles or less) would clear it up. Also holding the RPMs elevated at say 2-3k would free them up as well.

Thanks for the responses. It gives me more reassurance about just leaving it be.

I'm sure you're right that it's normal and not worth worrying about, but man that noise is embarrassing. It sounds like rod knock (though I know it's not). It'll make selling it more difficult once the time comes too.

I've been changing the oil with M1 twice a year for two and a half years at this point so I've given up hope that something sticky just needs to be freed up. I only put on a few thousand miles between oil changes. :nix: I tried Liqui-Moly Pro-Line Engine Flush right after I bought it hoping that would help with no result, too.