M272 Balance Shaft issues exist outside the published range

Premature failure of the Balance shaft on the Mercedes M272 engine is a known problem.   Apparently the balance shafts were too soft and so they wear out quickly.   This was the subject of a class action lawsuit in the United States.   Over there, the shafts in affected cars were replaced by the dealer out of warranty.     This wasn’t the case here in Australia, although it is possible that a handful were done for good customers.     There is a service bulletin published by Mercedes-Benz that outlines the repair and the engines numbers affected by the soft M272 balance shaft.   Generally those engine numbers correspond to 2005 to early 2007 production.

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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