Finally M276 3.5NA engine teardown
Thread Starter
MBWorld Fanatic!
Joined: May 2018
Posts: 6,602
Likes: 6,549
From: Jakarta-Indonesia
2014 - W212.065 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
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.
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.
.
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
IDLERS DELIVERS RIP
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.
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.
Belt did get ingested to stop oil pump at higher RPM.
Serpentine needs maintenance kit replaced on schedule, not post mortem!
> AMAZIN' IDLERS....
We know the small idlers are barely guided by a tiny plastic insert, fastened lightly into aluminum head. The idler has the ability to quickly derail the belt off track.
Once the dry bearing is compromised by heat, the amount of wobbling vibrations loosens the long center screw... the rest is history!
Last edited by CaliBenzDriver; Aug 4, 2025 at 12:41 PM.
Out Of Control!!
Joined: Sep 2018
Posts: 14,666
Likes: 4,568
From: unbegrenzt
2017 GLE350 4MATIC
I replaced the poly-v belt on my W166 M276 3.5NAV6 engine and it was an easy 20 minute job.
https://mbworld.org/forums/gle-class...ml#post8544125
https://mbworld.org/forums/gle-class...ml#post8544125
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
SERPENTIME MAINTENANCE KIT
I replaced the poly-v belt on my W166 M276 3.5NAV6 engine and it was an easy 20 minute job.
https://mbworld.org/forums/gle-class...ml#post8544125
https://mbworld.org/forums/gle-class...ml#post8544125
The one thing I'd do differently is TENSIONER + idlers + belt kit.
A new belt on an old tensioner stays loose thus slips and gets overheated.
Conti belts are great!
Tensioners are built to carve a groove that matches old belt length.
Last edited by CaliBenzDriver; Aug 4, 2025 at 03:37 PM.
Thread Starter
MBWorld Fanatic!
Joined: May 2018
Posts: 6,602
Likes: 6,549
From: Jakarta-Indonesia
2014 - W212.065 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
I replaced complete set idler + 2 pulley + belt under 35,000KM.
Not so good the 2 pulleys due to my always high RPM.
The tensioner lost 21% of its tension, it is easy to measure .
https://mbworld.org/forums/e-class-w...ng-torque.html
=======
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
Torque values using AC Delco https://www.acdelco-tools.com/index....product_id=208
Not so good the 2 pulleys due to my always high RPM.
The tensioner lost 21% of its tension, it is easy to measure .
https://mbworld.org/forums/e-class-w...ng-torque.html
=======
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
Torque values using AC Delco https://www.acdelco-tools.com/index....product_id=208
