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Old 02-02-2012, 08:59 PM   #1
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272 Engine Balance shaft problems

Hi Guys,

Question mainly for Techs but obviously all comments welcome as usual.

We have had a customer in with a CLS350 with around 123k on it. Ended up diagnosing balance shaft problems. Stripped front and found the most horrendous wear ever, this major component was pretty round........not much resemblance to a cog/gear anymore. Anyway, we whipped the engine out (essential to remove the shaft) and replaced the shaft. Quite embarrasingly, we dropped a...mistake and one of the cam adjuster mechanisms' lost it's backlash pre-tension. Naturally, as it was our fault, we absorbed the cost and bought a new one (later part number) for the customer and built it back up. To be sure, we changed the cam position pickup as well as there was a later part number listed for that too.

Basic timing all good, double checked timing of cam adjuster magnets after engine ran and all good. (40 degrees and 305 degrees). Car drives well, did around ten miles and no engine management light. Prepped and washed car and went for test drive just before customer pickup. Final fault code check reveals a code for camshaft adjustment (will post the exact details later). We reset all adaptation values and engine light with codes for all four cams. Guided diagnostics is slightly odd and says "do not replace magnets" "Do not replace solenoids" Actuation test suggests no actuation of solenoids.

For information, the car now has three old cam adjusters and the fourth (Right Exhaust) is now a new part number, the number has been changed twice....

Additionally, there is a mix of cam solenoid standards as well, some later part numbers some original.

Customer is understanding for now but obviously both us and him want to get sorted asap. I suspect this will be an increasingly more common occurrance for Indies as cars without full service history probably won't be valid for Mercedes good will money as most have been up until now.

In summary, question is: Has anyone experienced problems with mixing the standard of cam adjustment component part numbers on these 272 engines?

All comments appreciated! Thanks in advance.
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Old 02-02-2012, 09:22 PM   #2
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You might be interested in this thread?? M272 and 273 Engines: The Judge Has Spoken - Page 2 - Benzworld.org - Mercedes-Benz Discussion Forum In particular this post #12 by an MB TECH [usa]

QUOTE:-

In the early days of this problem as the balance shaft on the 272 or the sprocket gear on the 273 started to wear the cam sensor would see this and put the cel on, but the engine was still running ok.

MB in their wisdom modified the camshaft adjusters and the sensors to allow for bigger parameters, a cheap fix and the cel did not come on again but the balance shaft continued to wear. However this modification (cheating really) allowed the car to reach the end of its warranty before total failure.



My guess based on the above and its only a guess is that the Engine ECU is experiencing some sort of "out of spec" comparison error between the old and new cam adjuster/ sensor signals and flagging an error. Does the fault code signify where the fault lies exactly??

Might be worth a trawl thro some of the USA forums--- far more big petrol engines "over the pond "than here.
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Old 02-02-2012, 10:25 PM   #3
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Thanks for that Grober,

I'm glad you found that one. We suspected the difference would be something like that. I can't imagine the ECU liking a mxture of parts, will consult the North American chaps and see if they can shed any light on it.

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Old 02-02-2012, 11:21 PM   #4
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there's also this which I referred to in a post some time ago http://www.motor-talk.de/forum/aktio...hmentId=681441
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Old 03-02-2012, 03:14 AM   #5
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Cheers Grober,

I had seen this and it may be of interest that the worn sprocket on our customers car makes the one on the SB look quite good, I'm surprised there was not a major failure in timing. Will post a pic later. Couldn't find a UK version of this either and TIPSs didn't appear to have any history, however, this American document is certainly useful.

Now, I have just noticed the folllowing on page four...........

h) Replace all four of the camshaft adjustment solenoids with A272 051 01 77 – this step applies only to Scenario 1.


Scenario 1 is our exact problem so I'm thinking this is our first port of call, we have two already from initial diagnosis but as soon as we found misaligned timing stripped for inspection.

Top tip for anyone else finding that issue, just take the engine out. Hard work taking the cover off in situ and the lump comes out of the CLS reasonably well.

Will keep you posted on progress!

Thanks again for pointing out the info, much appreciated.
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Old 18-02-2012, 10:40 AM   #6
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Quote:
Originally Posted by Mattyo View Post
Cheers Grober,

I had seen this and it may be of interest that the worn sprocket on our customers car makes the one on the SB look quite good, I'm surprised there was not a major failure in timing. Will post a pic later. Couldn't find a UK version of this either and TIPSs didn't appear to have any history, however, this American document is certainly useful.

Now, I have just noticed the folllowing on page four...........

h) Replace all four of the camshaft adjustment solenoids with A272 051 01 77 this step applies only to Scenario 1.


Scenario 1 is our exact problem so I'm thinking this is our first port of call, we have two already from initial diagnosis but as soon as we found misaligned timing stripped for inspection.

Top tip for anyone else finding that issue, just take the engine out. Hard work taking the cover off in situ and the lump comes out of the CLS reasonably well.

Will keep you posted on progress!

Thanks again for pointing out the info, much appreciated.


Was this resolved in the end?

Would you mind sharing the approx time taken on the repair and prices for the components?

I'm contemplating buying an M272 driven car in the near future so would be good to have a heads up on this issue as I believe it is likely to be a more common occurence as these cars hit higher mileages. From my basic understanding it seems like this failure is inevitable on all M272/3s before Mercedes started building the cars with upgraded parts in c. 2008.
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Old 06-03-2012, 12:51 PM   #7
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Hi Guys,

Just thought I'd stick an update on. Car now running well but only after changing the chain and two cam adjusters. If anyone else has this engine code, M272 or M273, do not ignore the engine management light! There are two codes that indicate the problem and the earlier you catch it, the better. I have heard of it being left so long that the debris trashes the engine completely!

Also, exhaust the dealer as an option, the guys have all been briefed that it may occur as a problem and I believe there is a likelihood of goodwill payments from them.

If it is caught early the main parts and labour are around 1400-1700 depending on how far you go and what you find........beware, the cam adjusters are 500 each! On the one that we did, the chain/timing had slipped as the balance shaft sprocket was really worn, hence the extra problems.

Struggling to judge how bad the problem is in the UK as our local dealer has never done one but I spoke to a few guys down south that have done several! This was a 2006 and all of the components have changed part number twice since then. I'm wondering if the new cam adjusters/parts give a greater range of movement as the customer did comment on it sounding a little bit beefier at higher revs "on cam".

I wouldn't let it put you off those engines completely though, they are really smooth and pretty quick!
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Old 09-07-2012, 05:36 PM   #8
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What is the approximate cost for the parts and how much labour is involved ?

Have had the CEL light on for a couple of months now but car doesn't feel any different.

Also is this a job for my local friendly mechanic bloke (he's not MB) just does a lot of my servicing on other cars
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Old 25-10-2012, 05:53 PM   #9
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Can anyone recommend a cheapish local mechanic Bath / Bristol to change out the balance shaft if I buy the parts from MB ??
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Old 25-10-2012, 05:59 PM   #10
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This is not a cheap job whoever does it...

Really its for an engine builder or a good technician who is proficient tackling engine rebuilds confidently.
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Old 25-10-2012, 06:32 PM   #11
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Hi Jay, I know it's not a simple job but spare cash is tight at the mo.

From what I understand its about 650/700 for parts and about the same again for labour and was hoping to find someone not too far away from me that might know what he's doing and who's not quite up to the VAT threshold as I can't re-claim that.

Last edited by Chrisk942; 25-10-2012 at 06:35 PM.
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