What's the highest mileage M278 engine achieve?
Thread Starter
Senior Member
Joined: Mar 2022
Posts: 267
Likes: 61
From: Chicago
Bi-Turbo E550 Coupe (W207)
What's the highest mileage M278 engine achieve?
Just curious if I should be selling my vehicle or not.
M278 engine is wonderful but reading all the stories of all the issues has me fairly concerned it will not last past 150,000 miles unless there's cases that folks can inform the community on without having major issues like the leaking sensors, coolant mixing with the oil, etc.
M278 engine is wonderful but reading all the stories of all the issues has me fairly concerned it will not last past 150,000 miles unless there's cases that folks can inform the community on without having major issues like the leaking sensors, coolant mixing with the oil, etc.
Senior Member
Joined: Aug 2021
Posts: 362
Likes: 186
2018 S560, 2004 SL500, 2014 S550 (SOLD), 2012 S550 x2(SOLD), 2007 CL600 (SOLD), 2007 S600(SOLD)
Just curious if I should be selling my vehicle or not.
M278 engine is wonderful but reading all the stories of all the issues has me fairly concerned it will not last past 150,000 miles unless there's cases that folks can inform the community on without having major issues like the leaking sensors, coolant mixing with the oil, etc.
M278 engine is wonderful but reading all the stories of all the issues has me fairly concerned it will not last past 150,000 miles unless there's cases that folks can inform the community on without having major issues like the leaking sensors, coolant mixing with the oil, etc.
Thread Starter
Senior Member
Joined: Mar 2022
Posts: 267
Likes: 61
From: Chicago
Bi-Turbo E550 Coupe (W207)
I’m currently at 112K for a 2012 W207. I love the color, prestine interior, and heads turning from many M157, N63, or other more expensive coupe drivers.
However now entering space which could be dangerous. I have replaced all the plastic coolant lines two years ago, and topped off my coolant recently. Keeping a careful eye, along with my indy Benz mechanic, on all things that could cause it to become a problematic engine such as oil leaks and coolant leaks.
All my electronic shocks, control arms, sway bar links, brake pads, and rotors are new with less than 10K miles so my coupe is ready to roll, just don’t want to be wiped out by an engine, engine mounts, or transmission issue. This car was meant to be low maintenance specific to those subsystems but in past year so many articles and mechanic videos on YouTube explaining the failures of the M278 engine have me considering whether to keep or not. I’d prefer to keep as I love the elegance and smoothness of the vehicle.
However now entering space which could be dangerous. I have replaced all the plastic coolant lines two years ago, and topped off my coolant recently. Keeping a careful eye, along with my indy Benz mechanic, on all things that could cause it to become a problematic engine such as oil leaks and coolant leaks.
All my electronic shocks, control arms, sway bar links, brake pads, and rotors are new with less than 10K miles so my coupe is ready to roll, just don’t want to be wiped out by an engine, engine mounts, or transmission issue. This car was meant to be low maintenance specific to those subsystems but in past year so many articles and mechanic videos on YouTube explaining the failures of the M278 engine have me considering whether to keep or not. I’d prefer to keep as I love the elegance and smoothness of the vehicle.
Last edited by ibbij; May 8, 2023 at 02:06 PM.
Senior Member
Joined: Aug 2021
Posts: 362
Likes: 186
2018 S560, 2004 SL500, 2014 S550 (SOLD), 2012 S550 x2(SOLD), 2007 CL600 (SOLD), 2007 S600(SOLD)
I’m currently at 112K for a 2012 W207. I love the color, prestine interior, and heads turning from many M157, N63, or other more expensive coupe drivers.
However now entering space which could be dangerous. I have replaced all the plastic coolant lines two years ago, and topped off my coolant recently. Keeping a careful eye, along with my indy Benz mechanic, on all things that could cause it to become a problematic engine such as oil leaks and coolant leaks.
All my electronic shocks, control arms, sway bar links, brake pads, and rotors are new with less than 10K miles so my coupe is ready to roll, just don’t want to be wiped out by an engine, engine mounts, or transmission issue. This car was meant to be low maintenance specific to those subsystems but in past year so many articles and mechanic videos on YouTube explaining the failures of the M278 engine have me considering whether to keep or not. I’d prefer to keep as I love the elegance and smoothness of the vehicle.
However now entering space which could be dangerous. I have replaced all the plastic coolant lines two years ago, and topped off my coolant recently. Keeping a careful eye, along with my indy Benz mechanic, on all things that could cause it to become a problematic engine such as oil leaks and coolant leaks.
All my electronic shocks, control arms, sway bar links, brake pads, and rotors are new with less than 10K miles so my coupe is ready to roll, just don’t want to be wiped out by an engine, engine mounts, or transmission issue. This car was meant to be low maintenance specific to those subsystems but in past year so many articles and mechanic videos on YouTube explaining the failures of the M278 engine have me considering whether to keep or not. I’d prefer to keep as I love the elegance and smoothness of the vehicle.
Engine mounts are basically a wear item and with 4MATIC I can see it being a concern.
Senior Member
Joined: Aug 2021
Posts: 362
Likes: 186
2018 S560, 2004 SL500, 2014 S550 (SOLD), 2012 S550 x2(SOLD), 2007 CL600 (SOLD), 2007 S600(SOLD)
Gotcha. I was mixing up the sedan and coupe as I believe the W212 sedan only comes in 4MATIC in which case the engine mounts are a pain. If your W207 is RWD then I'd like to think that engine mounts would be a relatively easy job and wouldn't break the bank. Those videos are concerning. Do you have a rattle on startup?
Just FYI Mercedes issued a warranty extension on M278 cylinder heads for 12 years/120k miles. If you ran into misfire issues you could potentially have the heads replaced at a dealer free of charge.
Just FYI Mercedes issued a warranty extension on M278 cylinder heads for 12 years/120k miles. If you ran into misfire issues you could potentially have the heads replaced at a dealer free of charge.
Thread Starter
Senior Member
Joined: Mar 2022
Posts: 267
Likes: 61
From: Chicago
Bi-Turbo E550 Coupe (W207)
No rattle on startup…smooth and sounds wonderful.
This is what I’m working with:
https://mbworld.org/forums/e-class-c...cessories.html
https://mbworld.org/forums/e-class-c...ting-e550.html
This is what I’m working with:
https://mbworld.org/forums/e-class-c...cessories.html
https://mbworld.org/forums/e-class-c...ting-e550.html
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Thread Starter
Senior Member
Joined: Mar 2022
Posts: 267
Likes: 61
From: Chicago
Bi-Turbo E550 Coupe (W207)
Awesome! How have you done your maintenance schedule? Any regular intervals and special ways to check the health of the engine?
I’m at 124k miles / 200k km and want to get to at least another 150k km.
I had to do replacement of all the plastic coolant line parts and I get regular oil changes. I have checked regularly oil that it’s not seeping into the ECU wiring harness. I do have an unusual issue with small amount of coolant reducing so I may have a small leak in the system somewhere. I just hope it’s not seeping into any internal part of the engine as I have watched videos on YouTube that coolant and oil can end up mixing if the gaskets fail.
I’m at 124k miles / 200k km and want to get to at least another 150k km.
I had to do replacement of all the plastic coolant line parts and I get regular oil changes. I have checked regularly oil that it’s not seeping into the ECU wiring harness. I do have an unusual issue with small amount of coolant reducing so I may have a small leak in the system somewhere. I just hope it’s not seeping into any internal part of the engine as I have watched videos on YouTube that coolant and oil can end up mixing if the gaskets fail.
Out Of Control!!
Joined: Apr 2019
Posts: 11,951
Likes: 6,795
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
small slow leak...
check the front radiator CRIMPS all around for leaks - Its a good idea not to extend the life of cheap radiator because of killer internal mayo-mixing issue.
Amazin' radiator leaks both internally and externally. It's a lot easier to replace than a heater-core
Amazin' radiator leaks both internally and externally. It's a lot easier to replace than a heater-core
Last edited by CaliBenzDriver; Aug 2, 2024 at 01:32 PM.
Out Of Control!!
Joined: Apr 2019
Posts: 11,951
Likes: 6,795
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Timing cover seal... end of life extension
This failed coolant seal is between Bank2 engine head and front timing cover.
> CANCELING ROOT CAUSE:
This location sees the hottest oil and the hottest coolant... can we reasonably says that it is affected by extreme heat soaks?
The weak seal destroying the engine is not the cause but a consequence. Replacing seal EARLY only moves the burning heat issue over to the next weakest seal.
What if we could curb these conditions back to nomal 200F heat without any extremes ??
The extreme heat source is the limited pistons cooling to "save gas".
Check out this thread about normal oil pressure....
The cheap item that can help protect engine life is having a working coolant CAP that reliefs coolant pressure without straining the weakest engine seals.
Last edited by CaliBenzDriver; Aug 2, 2024 at 05:47 PM.
Newbie
Joined: Sep 2008
Posts: 8
Likes: 0
E550 w207
mine lasted 137,000 b4 cylinders 5,6 were scored.
2012 E550 coupe, babied it. 6K oil changes. Always Liquid Molly. 45K mi oil through the solenoids into wiring harness. 80k mi blown driver side turbo, dropped the motor to replaced both. 137k mi flashing CEL car stuttering, leak down compression showed some minor loss on cylinder 5 and 6. Scoping confirmed cylinder wall scoring. Done. Not including consumable costs such as radiator, alternator, steering lock solenoid (which is no longer available. had to get mine redone electrically). Car is still pristine so debating the whole rebore\sleeve option or just ditch it.
