About 5 years ago,  I was in the market for an E350 Wagon for my wife.   We wanted an occasional 7 seater that wasn’t an SUV.   Based on the service bulletin, we purchased a 2007 rather than the 2005 we were looking at.   The car we eventually purchased was well outside the known range of bad M272 balance shaft issues.

About a year ago, we started getting codes from the car indicating the the timing was off in one bank.    Based on the knowledge that the car was outside the affected range, we started looking at other sources for the problem.   First, I tried changing the magnetic adjusters.   These are a known problem also and an easy fix.    After a while, the light came on again, so next I tried the sensors.   This didn’t have much of an impact.    I took the car in to be looked at, and it was suggested that the broken intake manifold flaps may be to blame, so I had those fixed too.    Again, same problem.

From there I was becoming more and more convinced that despite being outside the published range, I had a bad M272 balance shaft.   I took the car to another shop who had done hundreds of these repairs to check.   they took off the cam covers and were able to spot the worn balance shaft.     The quote to fix is $6,000 which is in line with other good independent shops in the area.   This includes 24 hours of labour and taking the engine out completely.

As can be seen above, the part is quite innocuous, but a lot of the engine must come apart to change it.    As well as what is pictured above, normally the head gaskets, timing chain and sometimes sprockets are changed.

I suspect the M272 balance shafts are harder after the known range, but still fail.   Our car now has almost 180,000km on the clock.   It had about 170,000km when these symptoms started occurring.  I suspect these issues could also affect the M273 V8.   Those engines do not have a balance shaft, but they do have an idler sprocket there.   That sproken was also known to be soft in the early engines.

I have been thinking long and hard if I will fix the issue.   I have decided to fix it.   Used car prices have gone so high since COVID that the car is worth more than what we paid for it 5 years ago.   Buying a different S211 would also have the balance shaft risk, plus not have the work I’ve done on this car recently such as rebuilt front end, intake manifold, rear air springs etc.   With used car prices the way they are, a S212 wagon is still more expensive than we would want to spend.

It will likely get booked in for the job in the first half of 2022.   While the update 211 is a good car,  there are a number of design flaws.    Obviously there is the balance shaft issue.   There is also the plastic intake manifold flaps, other plastic parts in the engine that don’t last very long, and rear air springs with a short service life.

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The first set of codes were complaining about the correlation of the camshaft and the crankshaft on one bank.   I had previously changed the magnetic actuators, which temporarily fixed the problem.    If the car didn’t sit outside the engine numbers with the soft balancer shaft, I would have probably assumed that this was my issue.

The second set of codes were about the tumble flaps in the intake manifold.   They are made from plastic and the hot engine makes them brittle and fail.   Mercedes will try and sell you a whole new intake manifold, but there are aftermarket solutions to replace the plastic with metal.   You would have thought Mercedes-Benz would have learned by now about brittle pastic on their engines.   I didn’t want to tackle this one myself, so had it done by a professional.   While the car was there having this and the front suspension rebuilt, we checked the codes.    The various camshaft codes were there, but the actual values of the camshafts seemed correct.

That got me thinking that perhaps it was the sensors sometimes giving bad readings.   I probably should have changed them at the same time as the magnetic actuators.   In any case, the M272 camshaft position sensors are not particularly expensive and very easy to change.

As the M272 is a DOHC engine, there are four sensors.   The right hand sensors are slightly harder to change, but each one can be done in less than five minutes.   The new sensors came with o-rings, which was good as the old ones were very hard.     I don’t know what it was, but there was some kind of residue on a couple of the sensors.   I doubt it was impacting how they worked, but at least the new ones do not have it.

After replacing all four sensors and re-setting the codes, I was able to drive for 15 minutes without the check engine light.   It’s been a long time since that was possible.   The proof of the fix will be if the light is still not illuminated after a couple of weeks.   It was worth trying as four M272 camshaft position sensors are not expensive and the time to change them is negligible.

Update 22/9/21:  The Check engine light is back on.   Only lasted two days.    Back to the drawing board.   

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I got out my scan tool to work out what was wrong.    The main code that seemed relevant was P0016.   This was complaining about the correlation of the crankshaft and camshaft positions.    There was a more detailed one that indicated the right cylinder bank was too retarded.   The M272 camshaft adjuster is a known problem on these cars.   Apparently the part has been upgraded since the engines were new.   It is also the same system on the M273 V8 engine.

From what I read, the M272 and M273 engines use these magnetic camshaft adjusters to control the variable valve timing.   They obviously contribute to the good power these engines make for their size as I could notice the difference with three cylinder retarded.

Its not a big job to change these out, at least on the V6.    I would imagine the v8 is also pretty easy, just a bit less room.    FCP Euro sell a kit which includes the four genuine M272 camshaft adjuster units as well as some other parts to do the job.    All the instructions I found on the internet assume that the oil cooler and power steering reservoir must be removed to get at the adjusters on the left hand side of the car.     I also found a video that indicated that the oil cooler could be left in place if the job was done with an E8 Torx spanner rather than a socket.    As well as the kit, I also ordered a set of Torx spanners.

This spanner was a really good tip.  I used it quite a lot and found that I didn’t even need to remove the power steering reservoir.    This made the job a lot simpler.   I started on the harder left hand side.   The first thing to do is to disconnect all four M272 Camshaft adjuster units.   There is a grey locking tab that must be pushed up carefully with a flat heat screwdriver.   Then, to actually release the connector you need to push down around this locking tab.     I also found it easier to remove all four connectors to the camshaft position sensors.   Mine were quite brittle and the two that still had locking tabs don’t anymore.    Also, to get to the upper adjuster on the left hand side, I had to remove the corresponding position sensor.

Once you’ve done the hard side, the other side is really easy.   There is almost nothing in the way of these bolts.

Each of the M272 Camshaft adjuster units is held on with three E8 torx bolts.   I found the only a couple of them could easily be removed with a socket and the E8 spanner was really useful.   As I mentioned above, the spanner meant I didn’t need to remove the oil cooler or even the power steering reservoir.

The old sensors were quite dirty.   For an engine that has only 172,000km and has been maintained as per the factory service recommendations, there was more sludge on them than I would like.    I think perhaps the manufacturers have stretched out the oil change intervals too long.   This sounds good for buyers as it makes them appear to be cheaper to run, but the idea of a modern Mercedes being cheap to run is laughable.   A couple more oil filters and a bit more oil would be a drop in the ocean compared to the real cost of these cars.

This job is quite simple and easy for home DIY.

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Crankshaft Position Sensor failures are common in modern Mercedes Benz, and the symptoms pointed to a faulty sensor.    Doing some research, changing the M272 Crankshaft Position Sensor didn’t seem to be a massive job, so I ordered one.

This job isn’t particularly hard, but it is very fiddly.   Many of the write ups on the Internet refer to the M112.   This is similar, but there are some important differences.    On both engines, the first steps are to remove the engine covers and mass airflow sensor.

This provides the room to somewhat get to the sensor, which is on the right hand rear of the engine.   I found I wasn’t able to see the sensor, but you can feel it.   The biggest challenge was determining what kind of bolt was holding it down.   Most say that it is an inverted Torx E8.   Some others say it is a TX27 Torx and others say a TX30 Torx.    At least in the case of the M272 Crankshaft Position sensor on the E350 wagon in 2007, it was a TX30.   As you can’t actually see the bolt I wasted a good 45 minutes trying different sockets until I was able to get one that worked.    It is easy to get a torx bit wedged between the housing of the sensor and the outside of the bolt and think you have it on properly!

There is almost no clearance on the right side of the engine, much less than the left side.   I can only imagine this job is much worse on smaller cars like the C class.

I found once the bolt is removed, it is easy to remove the sensor.   Replacement is much easier than removal, and overall I had the job done in about three hours.   It should probably take about 30-45 minutes!

Before I started the car for the first time, I cleared the codes.   After a brief test drive, the code has not re-appeared.   On first start, the car ran rough for a few seconds and then settled down to a smooth idle.   If I was doing this again, I would know to use a T30 (most sites say the other ones), so I could probably do it in about half the time or less.    It is probably a job that would not be that expensive to take to a mechanic, but my wife uses this car every day, so it was easier for me to do the repair in the evening.

I will see in the next couple of days if this has truly fixed the problem.

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This was enough to put me off buying a car I would have otherwise bought.   Most likely I’ll be looking for an ’04 or ’08 model instead. Late 2007 models are also generally fine.  Its a shame as it was a nice car.  From what I read, repairing the M272 balance shaft means a partial disassembly of the engine and at least $7,000.  The dealer was also unwilling to let me have a mechanic check to see if the job had been done.   That was a showstopper for me.

The link to the Topklasse forum above also contains the factory documentation to look up the engine numbers of affected cars with this M272 balance shaft problem.  It also outlines the scope of the work required if such a car is to be repaired.  The early build M273 V8 engines also have problems, although not as severe as the V6.  There was a class action lawsuit in the USA that provided relief to those owners.

Update January 2017: I later purchased a 2007 model E350 Wagon that falls outside the affected engine numbers.   The Wagons can be hard to find as they were more expensive than the equivalent SUV.   They are a much better car though.

Update December 2021:  Turns out you can have Balance shaft issues outside the published range.   My car is now affected by this issue and is well outside the engine numbers listed.

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