He only failed to know the removal of the front timing cover uses those small dowel.
Overall this is very clear video

The M276 is too reliable that nothing failed so they can't ever make a tear down video

I really didn't understood how someone was able to get soooo much debris inside the oil pan...

Checking the dipstick but wiping it with a cloth full of sand and doing it often (just kidding) but you get the idea. Or they have a terrible oil filter, or terrible air filter, or terrible (you get the idea).

Thank you Surya for sharing this review.

This Canadian guy usually has smart engineering reviews.

I am ondering how the "indestructible M276" failed...

Year, mileage and vehicle model for the video?

Its a one-off unusual failure.

This 276 engine swallowed its serpentine belt.

Shredded pieces plugged up the oil pick up.
Oil starved bearings got overheated and spun...
game over.

This is a biturbo version of the same engine; it was driven through water and took a sip.
I'm a real fan of this guy's work.

I still wonder why video guy said it is serpentine belt debris
There is no way serpentive belt can enter our oiling system.

There is no data what mileage and what type of MB this engine comes out of, except it is a 4matic.

I haven’t heard this from Benz folks, but BMW N52/N54/N55 have a history of ingesting serpentine belts through the front main seal. Step 1 is OFHG leaks oil onto belt, step 2 is belt slips off idler pulley, wraps around crank behind main pulley, step 3 belt is wound through front main seal.

There are now aftermarket plates available for covering the front seal, to prevent such an occurrence.

I wonder if something similar (although rare) happened here.

WOW !!!!
That made so much sense, thank you.
This is the front crankshaft seal, brown color



Item 20 is crankshaft seal. Item 90 (2pcs) is the dumb-azz o-ring for coolant.



I have this seal for future use where I will need to replace 2 dumb-azz coolant o-ring #90 at this main timing cover to engine.


.





So the sepertine belt somehow accumulated at the crankshat behind the main pulley and it get fatter and fatter and push into the crank oil seal,
landed at timing chain region



This timing chain region has opening to oil pump/oil sump
This is M276.8 upside down, oil pump is up. M276.9 is identical for this region.





This reminds me of outboard motors, its tranny or lower case we call it, IF fishing line stuck on .....it can cause the oil seal to leak and water enter the oil holding region of the
lower case and bye bye lower case ( tranny ). This is small but tough nylon fishing line....imagine a serpentine belt







The owner must have neglected the serpentine belt or his belt tensioner went limp and thus serpentine belt can come off its groove.
Serpentine belt tensioner does loose its pressure value over time.
Or even the 2 plastic pulleys can crack and release the belt, it is plastic afterall.

My belt Tensioner, at maximum 36,000KM and 8th year of age, back in 2022.

Tensioner, to counterclockwise it a tiny bit to remove tight tension to belt.
OLD = 35 Nm
New = 40 Nm

Tensioner, to hit full stop ( spin counter clockwise ), spring maximum power.
OLD = 56 Nm
New = 71 Nm


The 2 pulleys :
While the bearing is steel, the actual frame of the pulley set is plastic.
The bearing inner OD is working against a sort of washer, made of plastic I label the washer as azz-hole.
Overall it is plastic strenght is what being relied upon.




Approx 0.05mm of that azz-hole plastic washer gone as wear and tear for 36,000km. I do not know what is a typical clearance limit, but I guess 0.1 mm is already a lot.







.


.

So the bottom line is ...INSPECTION AND MAINTENANCE .
Simply imagine your engine is a naked girl, thus you may want to peep more often at engine bay ...LOL.


Serpentine belt on M276 non turbo is so openly visible, easy to inspect.
On M276 3.0 Turbo its blocked by the aftercooler about 40% of total view.

Great to see detail about the M276 3.5NAV6 engine.

Poly-v belt replacement is easy on this engine. 20 minute job, or less.

the belt is not the root cause!
An external condition causes belt to fall apart:

• seized water pump
• weak tensioner spring
• oilyness slippery track
• failed idler nearest to A/C compressor
• combination
• ...

Belt don't normally expire... tensioner is the ultimate killer. It allows belt to slip under compressor load.

This car being Canadian 4M: there a chance Winter heat cycles help speed up failure.

Engines eating up the V-belt is a first one for me... it surely falls under the very weird category. Still I would assume one would stop the car once all the accessories go dead instead of keep running it until the engine seized.

The engine is basically EATING UP owners' money

I know right : )

Ya poor engine : (

and... they say water is essential to living things... oh right... it is not a living thing : )

Wish we have the mileage of that thing but I see 200,000 KMs M276 examples still running very well in Canadian climates. I know because I am Canadian.

Exactly, I heard the M256 engine is way harder to replace it.

Thanks for the insight!

I wonder if we can comment on his video and maybe he can reply to us with the information we need? Maybe link this thread as well. Someone do the honours, please : ) ?

Thanks for the informative post as always!

Thanks to JC for the fresh I Do Cars link.......

2nd similar M276 death from seperntine belt ingestion via front crankshaft seal....wow.

Leaking oil weakened the belt........ double wow, because many of them M276 has leaking mini VVT window


.

Excellent video, as are all of his teardown videos. It would have been nice to have this video 5 years ago!

New-to-me failure mode. Apparently from other comments, not unique to MB.

Oil leaks (front cylinder head covers, common) + oil spills (during oil change) --> oil contaminated serpentine belt --> weakened belt --> failed belt from chemical attack --> belt ingested by spinning crankshaft --> belt pushed front crankshaft oil seal into oil pump chain --> oil pump chain pushed off drive sprocket --> zero oil pressure --> seized main crankshaft bearings

Preventive action: fix oil leaks promptly, use a funnel to avoid spills, regularly replace serpentine belt, pulley and tensioners.

Seems like the block has iron liners - does anyone agree with this after watching the video?

Good to see 4-bolt cross-bolted main bearing caps.