S-Prihadi

Gents,

When I look at MB EPC, I do not much look at engine internals. MB EPC drawings are very compartmentalized section by section and not a nice easy to view
to see what connects to what if for coolant and engine oil actual fluid movement.

I rather look at engine teardown and pay close attention to seals, gaskets and o-rings in use.

I was looking at M113K engine tear down due to DEEP HIDDEN located coolant o-rings leaking and causing engine oil dilution with coolant and I realized our
engine should have similar o-rings to allow coolant from engine block to cross the timing belt region and to the mechanical pulley driven coolant circulation pump.
This is the M113K video


These are the 2 equivalent o-rings on our M276

Above, when one remove the mechanical pulley driven coolant circulation pump, this is how the coolant channels look like.




So the coolant circ. pump resides on the lower timing cover.
In order for coolant to cross timing chain area which is engine oil lubricated area, there is a need for o-rings for the lower timing cover to mate with engine lower/main block.








If one has to go this far a job to replace the 2 o-rings, surely timing chain adjusters (3 or 4 units ) need to be replaced too while at it and probably all of those
plastic components timing chain uses, need to be replaced too. For timing chain, that will depends on the engine mileage + visual inspection,
if one deemed it to be stretched or worn out enough.

There are special pressed pins which are also the timing chain plastic guide installation pin and at the same time lower timing cover pin which requires the
sliding hammer like those for injectors, for its removal. Below :






I don't know if total removal of radiator + evaporator + aftercooler + oil cooler and front bumper can allow enough room to work this DAMN o-rings without actual engine removal ?

If I were to keep my car for 20 years, this o-ring wont last 20 years....that is a 99% chance for me that it will leak before my car 20th bday.

Damn, now this o-rings nightmare is an addition to the already long list.

EASY ONE
https://mbworld.org/forums/e-class-w...ot-2-them.html

NOT EASY ONE FOR 3.0 TURBO engine
https://mbworld.org/forums/e-class-w...r-painful.html

NOT SO EASY ONE FOR ALL M276 , due to subframe blocking the engine oil pan major assy
https://mbworld.org/forums/e-class-w212/872246-only-1-2-o-rings-away-total-loss-engine-oil-lubrication.html

S-Prihadi

Master Tasos has a very nice complete video on a W211 E55 using M113 with this o-ring leak and complete teardown videos.

E55 W211 AMG supposedly was built between 2002 - 2009.
Tasos video was in 2021.
So oldest this engine can be is at 19 years old during the complete failure ( broken and partial lost of the o-ring ) or youngest is at 13 years of age.
16 years old as mid age.

Part 1 - steps to verify if this is a head gasket issue or the 2 notorious timing cover coolant o-rings


Part 2 - the pressure test, for the 2 notorious timing cover coolant o-rings


Parts 3 - Inspection of the failed o-ring

Here in detail we can see the front subframe removed,power steering removed, engine is hanging on engine support bar.
Plastic bumper and its aluminum bar removed, all radiator + evap + etc etc removed , in order not to do engine out job.

I spoke to my indie and he said the exact same set up to Tasos if one do not want engine out set up.


Part 4

If I hear it correctly, Tasos mentioned that M157 equivalent coolant 2 o-rings are not located like M113 ( or M276 ) inside the timing chain lower cover.
It is outside of timing chain lower cover, so if the o-rings leak it is not going to go to engine oil region....that is nice.

At 1:13 ( part 4 ) He also mentioned that this M113 o-ring groove design has no inner diameter lip/flange to help maintain o-ring shape like how M157 has a bit higher inner lip.
Its true of what me mentioned, o-ring groove design in M113 is bad. Too bad MB repeat the same M113 sh-iet in M276.
This is basic o-ring groove design guideline for face seal which is the duty of those o-rings in discussion :
https://www.marcorubber.com/o-ring-g...-face-seal.htm
Notice how the OD and ID of an o-ring has to get similar support all around by the lip/flange.
Parker Hannifin o-ring book is also a great source for o-ring 101.

I have a a few very expensive well engineered underwater camera housing from compact to full frame DLSR cameras from Nauticam, made of aluminum.
I do observe how the designer design o-ring grooves as my camera safety depends on these o-rings. The o-ring groove design is good.
All of my UW housings are 100 meter rated or 10 BAR, which is 7x higher pressure than our MB 1.4 BAR coolant pressure rating.

We are blessed now with utube having much more content than 10-15 years ago to help us visualize and learn of similar design and its weakness,
or service-able components no MB maintenance manual will ever discuss but will need to be replaced due to aging.... for those having 10 years old car
or would want to keep the car beyond 10 years.

If anyone is deep into o-ring material science and its compatibility to coolant, attached is a good read.
Elastomer Service Life Prediction in Organic Acid Coolants.pdf an SAE paper.

S-Prihadi

M276 owners has another little extra work.
To remove harmonic damper pulley, which is a must if lower timing cover is to be removed, we need flywheel locker tool.
M276 pulley design does not allow the common pulley spoke locker tool to be used, so flyhweel lock is what to be used.
attached the 2 WIS
The tool is similar to this : http://www.jtc.com.tw/product/?mode=data&id=2165&top=2
I must shop around for this tool, M276 compatible one.

I believe M276 has 2 starter motor install locations, each for RHD and LHD market.
So we use the flywheel locker tool on the side without the starter, just a cover plate.

200Nm + 180 degrees for pulley bolt is not a joke, that is high torque. The +180 degrees is the high torque, 200Nm is decent.
130Nm is W212 wheel bolts spec as reference.
If one instead uses the camshaft locking tool set and that means timing chain is to fight 200Nm + 180 degrees, I bet the timing chain will be distorted if not accelerated shorter lived.
I already have the camshaft locker tool and VVT oil solenoid big torx
Something like this : https://www.aliexpress.com/item/1005001630991080.html

So front crankshaft seal is another good one to replace too, while doing this job.

S-Prihadi

So sad........ so pissed .....so mad , me

I been reading the WIS over and over again............ this 2 flat seal o-ring will need me to remove these to access :

01. All injectors.
02. HP fuel pump
03. Surely cylinder head cover, which so happen to be also camshaft bearing journal top part.
04. Small VVT cover and main timing cover
05. All of timing chain & its guides and its idle gears
06. All of VVT sprockets
07. Damper pulley/harmonic balancer
08. Intake manifold and throttle body
09. All of serpentine belt tensioner + pully
10. Mechanical Coolant pump
11. Thermostat & its housing
12. Aftercooler
13. Alternator
14. Radiator fan - for more access
15. Radiator - for more access
16. HVAC condenser....hopefully not if item 15 and 14 has allowed enough space to work.
17. Other component I may have missed , like front crankshaft seal which is at timing cover .....


I done calculation and while there, timing chain guides + chain tensioners best be replaced.
There are two timing guides which must be bought with the chain...dugghhh
Proper injector seals & clip install tool is not cheap.





Item 16 is only US$2.00 genuine at Ebay. This is the FLAT SEAL...the big sucker !!




.





.
There was as a TSB for this similar duty seal on M278 and M157 engine. Damn. So early in 2013 ????
I think if owner discover it too late and a mere 250-500cc of coolant into engine oil, the engine may be totaled and junked...... and the actual cause may not be known.










So much work I must do, and waste my money too for parts I have no choice but to replace them since I am there anyway.
I will surely get someone to help me, I won't do it alone all 100%. My hands/fingers carpal tunnel syndrome will kill me.



I am wondering : M272 has similar flat seal like M276. I mean M272 is older than M276, so probability of this seal leaking would be likely M272 owners to experience ahead of M276 owners.
I googled for coolant in oil for M272 and only get the issue with oil cooler gasket, the common one but I have yet to see the timing cover flat seal as cause of leak.




.

CaliBenzDriver

That's another good qualified engine killer you found.

I think HEATSOAK is involved in activating this guaranteed killer.
Heatsoak is the coolant temperature shooting up immediately after engine stop. Block is hot but coolant is no longer circulated by serpentine pump so temperature goes up with pressure... keyword: PRESSURE!

When my engine was superheated by limited oil circulation, since new it would always smell like coolant was leaking and the cap was not just venting because level was also dropping... amazing! 👏
Since we begun testing "normal oil circulation", not once it has smelled hot coolant during heatsoak at home. BIG DIFFERENCE THERE!

What I am rationalizing is that after cancelling "limited oiling" feature, we have eliminated chances of busting our coolant seals from overheated engine block.
Your cooling circuit is not going to see extreme uncontrolled heat soak stress.

The killer seal acts as a pressure relief. Less heat, less pressure: no venting.
We want to make sure the expansion tank vent cap keeps doing it's job to protect circuit integrity and not prematurely age shut. This little stack of plastic is super important to protect engine from self-destruction.

Sanity is restored.

S-Prihadi

Still no polymer o-ring will last to X year.
I must find my 1 year before X year

My math was like this :
I plan to keep car to 20 years...will I extend pass 20 years ? Maybe.

This 2024, the car is 10 years old, so anything I invest now in super-**** preventive maintenance should happen at year 10, latest year 12, so that I gain use for 8 to 10 years on those parts by 2034.
I mean my current data shows 10 years and 40,000KM is OK.

I really fear of polymer/rubber/plastic stuff breaking without warning....I do.

Since my engine M276.8 3.0T is based on M276.9 3.5NA for most component and the flat seal is the same , my alarm bell would be other M276 owners flat seal ...assuming they can detect coolant in oil visibly and not using
used oil analysis. If coolant leak super small say 250cc per 5,000 miles, maybe it wont be visible when and if most of the coolant water component has evaporated.

Hot temperature is a killer and I am in a hot tropical city and creeping traffic is really BAD BONUS for me.
Usually heat exposure by hours is what many polymer/rubber/plastic are tested to. In fact if we see Parker O-Ring handbook, there are lots of such information.

I have 2 radiator hoses failure so far, because these cars are kept between 7 to 9 years from brand new and that is the longest I have ever owned any cars, till now.
Now this E400 broke all records by age, not ownership years though.

One is my 2001 Toyota small 1.5L sedan. 100,000 KM of very abusive driving. Top radiator hose torn a bit. Caught in time as car engine was already shut down. Small leak.
2nd is my 2010 Ford Fiesta 1.6L, only 27,000 KM of normal driving and by year 7th the hose which failed is the coolant hose between engine block to HVAC heater core... almost totaled my engine. Big leak.
Both this car has no coolant level alarm. In fact dumb-azz Ford Fiesta does not even have coolant temperature dial gauge ..DUGGGHHH !!!!



This is as bad as it gets in terms of my average speed I been logging for my 200 hours oil change or 5,000KM target.


The highest I ever got was when I drive Jakarta-Bali-Jakarta ( near 1 month in Bali ) for like 3,000KM. There then I got 35KM/H average ...LOL, only 21.7 MPH average.


When my daughter was still in Indonesia, once per 2 days my car get to run. I told my driver to use my car. 3 cars to rotate use for 2 trips to school return per day + extra private tuition sometimes.
I was still able to get good 24KM/H average for the close to 5,000 KM / 200 hours engine oil life because 80% of the journey was using paid highway.

15,000 to 20,000 KM oil life. In 2019.




Heat exposure in hours of engine running should be the best indicator to guesstimate polymer/rubber/plastic life.
So far I can say I have a 2,000 hours data only as SAFE.

Exposure hours ( years ) discounting temperature can sometime be useful to for certain fluids handling I guess, if one knows the chemistry of the product well.

Say a USA car done 100,000 miles. Unless he is in NYC traffic all the time, I guess US cars can do easy 35 MPH average speed.
100,000 / 35 = 2,857 engine hours. Still, unless in summer, them cars do not get heat soaked engine bay as bad as mine.

Let see this middle of year 2024, how it goes. However, I must target mid 2025 as maximum wait to do these flat seal o-rings at timing cover

Other hoses are easy and shall be done this year.

S-Prihadi

I am so fu***d up.
I just realized I actually need to remove both cylinder heads to access the 2 coolant o-rings inside the big timing cover.
Good think I kept watching the video over and over again....while looking at my friend's M271.8





Here is why cylinder heads must be removed.

The cylinder head gasket actually is also shared by the big timing cover.
The two bolts I circled pink/red.



.


.



.Below red line is the start of cylinder head gasket sharing with timing cover top part.



In red is the area shared by cylinder head gasket.
In blue are the 2 bolts from cylinder head interior, we need to remove the small VVT window to access these 2 bolts.




.








I watched the video over again because now I am too ( my Indie ) will be replacing M271.8 similar duty coolant o-ring.
My indie tech guy told me don't risk it by NOT removing cylinder head on the M271.8 Turbo, as the cylinder head gasket on this engine also over-hang to timing cover by a lot.

The M271.8 cylinder head over-hang above the timing cover is wider too than M276. So now engine is out. Waiting for stupid delayed parts.
Green is the over hang. Red is the timing cover interface area to engine block and cylinder head.



You guys owning M276 for long keep or buying old one in the future, someday will need to replace those 2 coolant o-rings at timing cover.
So be prepared.

I think in the next 4-5 years ,we will be seeing 2009 W212 with M272 failing their o-rings at timing cover.


--------------------

I don't think year 12th is even good for me to do this, minimum year 14th or in 2028 to make it worthwhile while not endangering my engine from coolant
leaking into engine oil. By then my car maximum will be 60,000KM only, estimated 5K KM a year from today.

By then all valves will get new oil seal, all spark plug o-rings replaced, clean the always dirty intake valves, and all the other job while cylinder head removed.
My my....... so much work !!!!

chassis

@S-Prihadi where was your 2010 Fiesta assembled? CKD in Indonesia or imported from where?

Not a good design to require cylinder head removal to replace a coolant o-ring!

S-Prihadi

The Ford Fiesta was Thailand assembled.

Chassis wrote :
Not a good design to require cylinder head removal to replace a coolant o-ring!

Tell MB engineers that....
Most of MB engines with timing chain will be this sad case.
All you need is to see EPC and find each engine timing cover , the o-ring will be in the same page... and then look up on Ebay timing cover actual design.
After that, he who will keep the car to 20 years old can start being stressed

MB2timer

The reputation of the German engineered engine, is that of a Swiss engineered watch. The fine craftsmanship, the balance, harmony, all supposedly top notch. How do these flawless(by reputation) engineers, and master craftsmen overlook something so obvious to cause unnecessary and premature failure?

Excellent thread by the way to OP.

ChuangTzu

Management/governmental pressure. The engineers know what works "best" from a mechanical standpoint, but they have new, competing criteria for getting the design accepted. They now need to eek out even more ounces per mile of fuel economy, shave dollars off the engine design, and use crappier plastics because of their supposed lesser environmental effects. This part of the design process is nothing new, but the design criteria outside of the basic mechanical function are becoming much bigger contributors to the design process.

You know the engineers did not want to add the oil pressure reducing solenoid to the design, but when pressed to reduce fuel consumption by 0.01mpg, they had to bring something to the meeting. They probably thought the idea would get rejected, but management said send it. So they sent it. Management is also under pressure from government regulations and the need to meet a price point for the final car. A 1994 E320 had an inflation-adjusted MSRP of $92k. Nobody would pay $92k for a base E-class nowadays because of competition from other brands. A base 2024 E-class has an MSRP of something like $62k now. But the 2024 E-class has probably 10x the number of parts and functions, airbags in every surface, and much more powerful and efficient engines etc... It's a **** situation to be in, but I think there is no clear optimum solution. If I could buy a brand new W123 for a reasonable price, I would consider it, but even a 1983 240D had an MSRP equivalent to over $70k...

chassis

Great assessment and price comparison. While the E-Class over time, using the example above, has declined in price in real terms, the F-150 has generally kept pace with inflation. Several influences at work - MB has cheapened the heck out of its products (true) and competition in the luxury segment has gotten more challenging (true). MB is putting more electronic gadgets in their cars, while meeting tougher safety and emissions standards, at the expense of fit, finish, as-delivered quality and medium term reliability.

S-Prihadi

M271.8 engine. Inline 4 cylinder 1.8 Turbo.
W212 E200/E250 in Europe and Asia or W204 C250 in USA

Single deadly o-ring



.




.





So engine out is the best way, because also of the rear-azz located oil filter-oil cooler combo, which WILL CRACK too....because it is made of PLASTIC body...








14 years old, 93,000KM seal of oil cooler/filter combo.
The damaged one is the COOLANT side seal.













When it is rubber seal and plastic. DO BE AFRAID OF IT.

S-Prihadi

I think I am seeing a pattern here..........

We have not heard any M276 be it 3.5NA or 3.0 Turbo having failure on these 2 o-rings in discussion.





The 2010 M271.8 1.8L in line 4, which I told my friend to replace the similar duty o-ring, his o-ring is still decent after 14 years. See below.



....




But his oil cooler+oil filter housing typical flat metal gasket with embedded seal, already failing at the coolant side, 1 post before this.





The TSB on M278 is also the same type of seal. Item 20.







Like oil cooler/housing seal, this type of seal does not get good side support like o-ring having its own cavity.
Take a look at how the seal #20 on M278 becomes thinning and wide, because of compression and aging.






M276 3.5 NA





M272



..





.


M273






So, those flat type of seal seems to be shorter lived, by A LOT shorter than typical o-ring shaped seal.

CaliBenzDriver

Thank you Master Surya for this very interesting research topic of yours.

This is clearly one big genuine cause for concern for ppl with hot engines.


Cooling circuit is setup for juicy troubles Master Surya spotted.

​​​​​


mayo mixed up


coolant seals vs. oil seals...


amazin' coolant seal !!

You are right: "there's like a pattern here":
The coolant seals are wasted while the oil side looks new.
​​​​​​

> Could this be related to something we're already familiar with ?
-- coolant extremely hot
-- lubricant cooler than normal


I think this is at least good evidence of extreme temperature from poor cooling.

Now why is that so :

• Coolant/oil Thermostats jammed
• Burnt thin lubricant
• Ineffective oil squirting
• Reduced pressure oiling

Can removing extreme engine heat eliminate this issue??


Facelift M276-NA now uses a separated filter + exchanger. The mayo follows the coolant-oil heat exchanger now located above the A/C compressor.

++++ NO JOY..... ONE AFTER ANOTHER......
Guess what happens next, the radiator blows its mayo seal.

Understand the fix is the SOURCE OF HEAT, not the cooked seals or mayo mix. Even obvious, when we lay it all down the dots connect.

Until you address the root cause, it will keeps delivering timely repairs

I say we are to try....
MOD-2.2 on 10W40/15w40:
should be close to a perfectly matched viscosity.


+++++ WHAT'S IT CALLED ?????
This is what HEATSOAKED SEALS looks like.

Extreme pistons heat transfers into the engine block to steam non circulating coolant with engine stopped or idling. Caused by trapped heat.

Heatsoaks are cancelled by effective oiling.

S-Prihadi

I think it is not only the heat Cali.

Could be also other factors.
One thing for sure,a flat polymer seal receiving side , if without proper groove to limit its expansion seems to be the one having early failure.

2nd is how many thousand hours will the polymer seal material last in the coolant, from compatibility perspective.

Before year 2000, MAN diesel engine get compatibility warning for certain coolants towards certain hose material.




So the SNF type in question is actually Glysantin G30. Audi call that coolant G12+






Download Parker O-Ring handbook, it has VERY good information https://www.parker.com/content/dam/P...e/ORD-5700.pdf


Also imagine an elastomer seal embedded/bonded on a steel plate as a "gasket assy", these two materials expand differently. Good to watch below :



Best preventive I think for such flat seal is to replace it before it fails....but, when is the right age ???

CaliBenzDriver

We know the failure rate is an inverted bell shape.

So we don't want to delay until near catastrophic failure.

75 to 100kMi plus heat correction factor.

You know your twin turbo adds heat... so 60 to 80kMi is safe if failures start rising after 120kMi.


This repair only signs the faith of radiator for next failure. The high heat creates coolant pressure that gets relieved by the weakest seal.

S-Prihadi

I plan to do all these seals, gasket yada yada.... actually this year, but the work is too much.
I will do it 12th year, or 2026. By then my car would be maximum 50,000KM.
50,000 / 21 KMH = 2,380 hours.
In USA 2,380 hours would probably be x35 MPH x 1.5 easy life in cooler climate = 83,000 miles x 1.5 = 125,000 miles