Tgiang

Cbr944

Hi. It's fairly simple to take the valve cover off and check engine timing - if the camshaft markers are even slightly off that will indicate a stretched chain. Note the C250 CGI engine uses a different timing chain to earlier M271 engines - it uses an "inverted tooth" or "silent" chain which supposedly is less likely to cause sprocket wear (the chain apparently rides up on the teeth as it stretches, rather than wearing into the teeth). If a check of timing shows the chain has stretched, it's fairly simple to replace it along with the tensioner. These would be worth doing as a preventative measure in any case, and could be causing poor starting if the chain has significant stretch.

You might also note the tensioner can be reused - there are YouTube videos showing how to reset these (it can't be reinserted once loosened without resetting it).

Cheers, David

Tgiang

Hello David. Thank you for that informative response. A few questions:

-what is causing premature life of the chains? I’ve seen chains with 400k miles in use and chain stretch at low miles is unusual. From what I’ve gathered, the adjuster contributes to this.
-can you test the adjuster besides pulsing it to verify activation?
-what mileage would be a good time to start checking for wear? I’ve seen various cases of delayed starting from 25k miles to 100k+ miles. This disparity is large and makes a diagnosis difficult. Profiling when members have experienced certain symptoms to when their chains have failed would help other members start taking precautionary measures.
-does our vehicle experience the crankshaft position sensor failure that has plagued earlier models?

Has anyone experienced chain stretch and/or failure and what were your symptoms leading up to this? Let’s help others start realizing that there is an issue, and how to address it. TIA.

cmriv

all the symptoms of timing issues can be directly related to oil change intervals. Correct oil filter being used. there are plenty of m271's running around with no issues ever. all the chains and adjusters i've replaced on m271 motor are customer who have purchased vehicles from a third party. this issue is common on vehicles that aren't well maintained.... NOw i'm sure there are cases where it's just bad parts/material defects however more times then not the culprit is user error.

cps failure is a past plague tbh. Very rarely will you see newer MERKS with cps issues however that doesn't mean it wont ever occur....

Cbr944

In my case my C250 had travelled well over 200,000km before I checked the timing chain and found it to have stretched. On replacing it, it had stretched about 10mm. This car was serviced by a MB dealer by the book since new. I don't think timing chain stretch is avoidable - some wear over time is inevitable. Poor oil or long change intervals could be expected to accelerate wear. That said, I still think the timing chain issues in the M271 EVO engines are much reduced compared to earlier M271s which used conventional roller chains.
To answer your question, I'm not convinced that wear of chains in these engines is "premature". It is a single row chain, which isn't ideal. I think best practice should be to preventatively replace the chain and tensioner on similar intervals to a timing belt, say every 100,000km/60,000 miles.
When I changed the timing chain I left the camshaft adjusters in place as the sprockets looked as new. This is even with a chain stretched by 10mm and after 200,000km of use.
I'm not sure the adjuster magnet is responsible or not for wear on M271 EVO engines. There is a locking pin in the adjusters which can cause problems if it breaks, apparently.

NZ-Merc

Hi
I replaced my 2008 C200 timing chain at 100,00km as part of my preventative maintenance plan, I figured that the original chain would probably last 150k and at that stage the sprockets would be worn as well so I replaced only the chain and expect it to last until 200k.

There was just a momentary rattle at start up with the old chain and with the new chain no rattle at start up, the length between the chains was around 3mm so not much stretch. I am the second owner and chain the oil and filter every 10,00km.

I replaced the chain buy joining it on to the old chain and drawing it through, to replace the tensioner in my model requires removing the lower front timing chain cover I chose not to do this as I dont want oil leaks later on.

The Magnets have there own oil leak issue and do not cause timing chain stretch.

With your starting issue if it was mine I would check the air filter and replace the spark plugs if that did not work I would book it in at the dealers for scanning on the Star scanner there may well be a high pressure fuel pump or fuel sensor faulty.

cmriv

I agree. Chain stretch is is always going to be apparent on engines because mechanical components are made to last forever.

ezshift5

Interesting thread here, amigos..........

So what are our conclusions...........??

Are the 2012 C250 4 cylinder M271 less prone to timing chain issues than earlier cars?

I sure like my updated CPO C250 coupe (but all this timing chain feedback is interfering with my sleep.


Best to all,


ez

michail71

Not so sure I can agree with that. My C250 failed and it had all it's prior services done on time at the dealership. How much bad maintenance can there be under 30K miles?

ItalianJoe1

Same components. The ones that get good regular oil changes don't seem to have unusual problems. The ones that are neglected, they need timing chains before 100k miles for sure. The rest of them, it's an issue with the gears failing internally, which the new ones are an updated part and does seem to correct it. The tensioners don't seem to fail on their own, but there's no real way to test them, and the replacement isn't so simple that i'd say just throw one in as preventative. The first sign of symptoms is usually after the chain is already noticeably stretched.

ItalianJoe1

The gears failed on yours, not the chain. That's a different issue and has to do with a poor design/materials and was corrected later on. The chains stretching is much more related to poor/lack of maintenance.

michail71

Ah, got it. I recall there was a bunch of low mileage 2013's that started failing a while back.

BeaverMjr

My 2013 failed at 60K. The tensioner pulley broke and the engine is now getting a rebuild under warranty. see my posts in the forum. in a week I should have my car back on the road.Its too bad MB has this problem.

ezshift5

C250 4 cylinder turbo M271 with 35,000. Any opinion on the type of driving influence on timing chain component failure? My CPO coupe gets 3500 miles accrued per year (with annual oil changes). I rarely use wide open throttle.

I would guess a low probability of a 60k failure...........................but it does happen............(Regret your failure, Beaver)

ez

BeaverMjr

Thanks. Luckily I kept all the receipts from lease inception. This way I could prove what work I had done not at the stealership. This way when I go to get rid of it, I have complete service history and can show that it was well maintained. Unfortunately, that might come sooner than later.

I'm curious what happened to the cars that had this problem in the past. Did they get repaired? Did the repair last? Any other major problems? Transmission? Other parts of the drive train?

cmriv

But who's to say the services were actually being done? If timing chain failures at or under 30k are happening, there must be a root cause is all i'm getting at. You could be right though, it could just be irony however there are plenty of M271's running around with low and high mileage with no such issues.

Tgiang

After having reported to the dealership under warranty the chain rattle and hard starts, they are now quoting 3800+ for a “faulty timing chain adjuster causing base timing to be lost when engine turned off.” This issue was prevalent in older m271 engines. It should not happen on a 70k mile c250w.