Tips on the x164 OM642 vehicles
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Joined: Apr 2011
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2021 GLS580 | 2011 ML350 BlueTec | 2009 Pontiac G8 GXP
I know that the OP is trying to be helpful, but if the OM642 is that fragile it never would have been offered to consumers in passenger vehicles. The OM642 is marketed to consumers just the same as a gasoline engines. There is nothing in the sales material or owners manual that says you can't do 1-4. They are marketing it as a general use vehicle. That means no special treatment.
I know of one successful law suit against a car manufacturer for marketing a "Track Ready" car that overheats if you actually drive it on a track and there are others pending. If the OM642 can't handle being driven to the grocery store or mall then it shouldn't have been sold as such and will likely come back on MB. Will it last longer if you do some of the OP's things? Maybe. But so would any other vehicle.
There does seem to be an issue with oil sludge but no one knows exactly what that issue is and why it is happening. Sure there are several examples on MBworld but there are thousands of OM642 based engines cruising along without the issue too. All we have is anecdotal evidence. If you look around you'll find examples of other modern engines and transmissions failing pre-maturely as well.
IMO the problem is our government's massive push for MPG. It has caused the manufacturers to push every component to its limit for that extra .1 MPG so that their overall fleet MPG goes up. This will naturally lead to more failures and guess who gets to pay for it.
I know of one successful law suit against a car manufacturer for marketing a "Track Ready" car that overheats if you actually drive it on a track and there are others pending. If the OM642 can't handle being driven to the grocery store or mall then it shouldn't have been sold as such and will likely come back on MB. Will it last longer if you do some of the OP's things? Maybe. But so would any other vehicle.
There does seem to be an issue with oil sludge but no one knows exactly what that issue is and why it is happening. Sure there are several examples on MBworld but there are thousands of OM642 based engines cruising along without the issue too. All we have is anecdotal evidence. If you look around you'll find examples of other modern engines and transmissions failing pre-maturely as well.
IMO the problem is our government's massive push for MPG. It has caused the manufacturers to push every component to its limit for that extra .1 MPG so that their overall fleet MPG goes up. This will naturally lead to more failures and guess who gets to pay for it.
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Joined: Feb 2009
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From: NW corner of CONUS
2008 GL 320 CDI, 2004 VW V10 Touareg TDI
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I have always wondered why the advice has been to leave diesels running rather than shutting them off. As a guy with an engineering degree, I can't for the life of me think of a good reason for this to be true, and that this is a hold over from the 'bad old days' of diesel engines when they were only in big rigs. I'd love somebody to explain it to me in mechanical terms. In fact, I think idling is *worse* for a modern diesel due to the DPF, which needs plenty of heat to prevent clogging, which it won't get at idle.
I do get that you want to let the turbo cool down before shutting it off.
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I have always wondered why the advice has been to leave diesels running rather than shutting them off. As a guy with an engineering degree, I can't for the life of me think of a good reason for this to be true, and that this is a hold over from the 'bad old days' of diesel engines when they were only in big rigs. I'd love somebody to explain it to me in mechanical terms. In fact, I think idling is *worse* for a modern diesel due to the DPF, which needs plenty of heat to prevent clogging, which it won't get at idle.
I do get that you want to let the turbo cool down before shutting it off.
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I normally chose to leave it idling until I am done!
The other reason many of the old diesels were left running in the big rigs is that, once thoroughly warmed up they simply ran better - and it took a few miles to get things back to smooth operation if they were shut off.
The amount of soot produced by an OM642 engine at idle is so small as to be negligible to the operation of the DPF.
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From: In my garage
E55, GLS450, GL63, GLE350
The reason to idle before shutoff is so the turbo will have time to cool down. It will extend the life of your turbo. Either that or get a turbo timer and it will take care of it for you.
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but the main reason is that cranking the diesel is not a happy affair for the piston rings and valve train. very high static compression makes for a lot of load on the timing chain, cam lobes, etc. think of it that way- the engine crank is about 200 rpm. when it catches all of sudden you are at 600rpms... the lash on the drivetrain is significant. repeat thousands of times and the net effect might be not to our liking.
but most importantly- every time you interrupt (and later resume) the flow of oil through a motor you risk forming hot spots (where oil doesnt reach quickly) and abnormal wear at those locations.
and i like the quiet clatter when the thing is just sitting too
Last edited by alx; Sep 22, 2017 at 08:32 AM.
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From: Albuquerque
'10 CL550, '12 GL550
The things you’ve heard about diesels in general are not specifically applicable to Mercedes diesels in general or especially the OM642.
I rather suspect you should consider the OM642 the most sophisticated diesel you’ve seen, although it’s possible bmw has something equal or a little ahead
In any event, I’m not worrying for a nanosecond regarding letting mine idle before shutdown.
The OM642 is also used in Sprinters currently, albeit at a lower state of tune.
Oh, and just helped step daughter buy a GL 450 and it’s WAY faster than my 320 and way smoother doing it. Too bad its highway mpg is same as my city mpg. ... but there’s payback..
Trivia: redline for the Audi diesels that won LeMans multiple times was 5500 rpm. Diesels physically can’t run any faster.
I rather suspect you should consider the OM642 the most sophisticated diesel you’ve seen, although it’s possible bmw has something equal or a little ahead
In any event, I’m not worrying for a nanosecond regarding letting mine idle before shutdown.
The OM642 is also used in Sprinters currently, albeit at a lower state of tune.
Oh, and just helped step daughter buy a GL 450 and it’s WAY faster than my 320 and way smoother doing it. Too bad its highway mpg is same as my city mpg. ... but there’s payback..
Trivia: redline for the Audi diesels that won LeMans multiple times was 5500 rpm. Diesels physically can’t run any faster.
