OM654 Engine

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simonjamesturne

simonjamesturne

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E270cdi
Does anyone have any info regarding the new 2.0 OM654 engine yet? I'm particularly interested in what's been done to address the OM651 simplex timing chain issue.

Experience has shown that the OM651 requires a timing chain replacement at around 80-100,000 miles, which is really difficult due to its location at the rear of the engine. Yes I know that you could just wind in a new chain, but really the tensioner should be changed too, which is a major job. This effectively gives most of these engines/cars a life of around 120,000 miles or 8-10 yrs.

Does anyone have any information as to Mercedes addressing these issues with the new engine, or are they again accepting a limited engine life?
 
As far as I can tell, the timing chain is still simplex on the OM654.

As for OM651 chain rattle/wear, I think it was an issue that afflicted early production engines, possibly up to 2012. MB appear to have made some sort of running change which fixed the wear - this was the view of a German taxi manager I spoke with a while back. As with all German taxi firms, they ran a large fleet of W212 E220's and on early models they had timing chain wear/rattle on start-up and in one instance a jumped chain/wrecked head. But from 2012 they had no more issues. If you also google the issue, there don't appear to be any newer posts on the issue. And there are A LOT of OM651 engine out there!
 
https://youtu.be/fpER7v0NtpQ

[YOUTUBE]fpER7v0NtpQ[/YOUTUBE]

Not sure about all the exhaust technology bolted to the engine rather than the vehicle body? Will perhaps lead to quicker warm up times but going to lead to some high underbonnet temperatures unless they have managed to get all that heat out the exhaust rather than radiating heat ???

Hows your German?

https://youtu.be/G0eaFhxTdK8

[YOUTUBE]G0eaFhxTdK8[/YOUTUBE]
 
The engine appears to be very difficult to maintain in that in order to access certain parts of the engine you'll need to remove the cat, turbo and a load of other items. The cam chain tensioner appears to be particularly difficult to access. It's almost as if the engine was designed as a 'sealed for life' unit with no provision for maintainance.
 
simonjamesturne said:
The engine appears to be very difficult to maintain in that in order to access certain parts of the engine you'll need to remove the cat, turbo and a load of other items. The cam chain tensioner appears to be particularly difficult to access. It's almost as if the engine was designed as a 'sealed for life' unit with no provision for maintainance.
Click to expand...

Isn't that the way things are going nowadays; 100k and you scrap it?

Ernie
 
I imagine this engine will be found in both fore and aft and transverse installations. When engines are built on a production line they appear to be relatively easy to work on as access is 360 degrees at eye level . Shoehorn the same unit into an engine compartment and its a different story. Perhaps if powerplants were truly self contained / easily removeable, as complete units --repair costs could be markedly reduced. As car designs increasingly package their powerplants into smaller and smaller spaces the maintenance aspect of same seems to be ignored. :(
 
The timing chain on the 651 engine is time consuming, but being at the rear doesn't really make much of a difference as it's still quite straight forward to replace.
No special tools needed
 
Pity they didn't move back to a duplex chain with the OM654, then it wouldn't have been an issue at all.

Also it looks like access for the OM654 is much worse than the OM651. Particularly the chain tensioner. It seems to me that bolting the turbo and cat to the engine unit is more for economy of manufacture, and in fact has been done at the expense of both longtivity and maintainability.
 
Perhaps much of the - how shall I put this -- "slimming down" ;) of engine components are made in search of reduced friction/ reduced inertial loads. Combine this with extracting more power from highly stressed increasingly small capacity engines and you have a recipe for decreased engine life. It would indeed be interesting to be a "fly on the wall" in the MB engine engineering development meetings where they have to juggle between MTBF and the next round of demands imposed by new emission standards.
http://www.vicorpower.com/documents/quality/Rel_MTBF.pdf
 
I don't know MB's rationale for moving away from duplex to simplex on the OM651 but it doesn't appear to have been an issue in the mid to long run, so if the set-up is the same on the OM654 then it should prove equally reliable on this engine.

My personal opinion is that MB still make solid diesel engines which outperform many others (look at the issues VAG have had with their 2.0TDI and to a lesser extent BMW and their 2.0 diesel issues). I previously had an S203 with the OM646 and it never missed a beat up to 137K. I too was cautious of the OM651 but after a lot of first hand research came to the conclusion it was good for the long run and have just bought a C250. I expect the OM654 to be equally as good (but of course it will likely have a few teething issues, which MB will fix).
 
Actually there seems to be a big problem with the OM651 after 100,000 miles.

http://www.mbclub.co.uk/forums/engine/170639-high-mileage-problem-om651-diesel.html

It looks like lots of independents are reporting this issue across all the forums. It's very apparent that moving to a simplex timing chain has caused a major weakness in these engines.

On a side point, does anyone know if the Renault based OM622/626 engines used in the C180 Bluetech are any better for longevity?
 
That link to a previous thread is getting on 3years old and is actually quite a short on replies. A quick google also reveals only a handful of other related posts on OM651 chain issues.
 
If its the same as the Renault R9M then yes it appears to have a chain at the front of the engine. Is this final acknowledgement that Renault have the best small modern diesel technology- apparently Mercedes think so? :eek:
Under the Skin: Renault R9M dCi 130
renault_r9m_700.jpg
 
I think you are right, when it comes to sub 2l engines. I also note that the cam chain is sensibly on the front of the engine, making it much much easier to change.
 
The link regarding the OM651 chain is cross linked to the "other forum" which has much to say on the OM651 chain failure modes (guides too apparently) which is quite recent. But I don't like linking directly to the other forum as it doesn't seem right to do so.
 
But again, the link to the 'other' forum takes you to a thread with no recent comments and not loads to start with.
The OM651 is now coming to the end of it's production cycle and on balance we've seen very few issues with this engine. Think of all the variants out there (fitted to cars and vans) and the thousands of engine-units produced and we've seen very few issues. The major issue was injectors on 220/250 variants and that was sorted relatively quickly and did not drag on. If there were widespread chain-stretch issues I honestly think we'd be seeing far more threads and news on the issue.
 
simonjamesturne said:
Does anyone have any info regarding the new 2.0 OM654 engine yet? I'm particularly interested in what's been done to address the OM651 simplex timing chain issue.

Experience has shown that the OM651 requires a timing chain replacement at around 80-100,000 miles, which is really difficult due to its location at the rear of the engine. Yes I know that you could just wind in a new chain, but really the tensioner should be changed too, which is a major job. This effectively gives most of these engines/cars a life of around 120,000 miles or 8-10 yrs.

Does anyone have any information as to Mercedes addressing these issues with the new engine, or are they again accepting a limited engine life?
Click to expand...
nothing wrong with timing chain on 651 my 220cdi 2012 has done 62k no noise nothing wrong
 
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