OM656D vs OM642

[such01]

Looking at purchasing a W222 with either the new flat 6 OM656 or tried and trusted OM624 engines. I've seen some 18 plate "high" mileage 100k+ OM656's for sale and wonder if these will be a good buy vs 17 plate OM642 with 70k on the clock.
Are there any issues with the newer engines compared to the old V6? What can I expect maintenance -wise with ongoing mileage over normal servicing?
Are oil cooler seals still an issue on the OM642's from 2016 onwards?
Anything else I should be looking out for on a 7 year old W222?

Thanks

 

[toteimerced]

All I can say is, all the 642 faults are well known, with effective remedies, with documented 70k, it should be good, I would have thought, the oil seals were altered to purple ones, from 2010 on I think it was, so that shouldn’t be a problem, either way, it seems the biggest problem with most Merc diesel’s, is the terrible AdBlue systems.

 

[such01]

All I can say is, all the 642 faults are well known, with effective remedies, with documented 70k, it should be good, I would have thought, the oil seals were altered to purple ones, from 2010 on I think it was, so that shouldn’t be a problem, either way, it seems the biggest problem with most Merc diesel’s, is the terrible AdBlue systems.

Thanks, my oil cooler is leaking again after the new purple seals were fitted in Nov 2018 - I'[m hoping this not an issue with the new seals. Would the adblue system still cause problems with proper use ie high mileage motorway? If mapped out would it still a problem? thanks

 

[ALFAitalia]

Looking at purchasing a W222 with either the new flat 6 OM656 or tried and trusted OM624 engines.

Straight 6.....not flat six.....thats a very different thing.

 

[such01]

Straight 6.....not flat six.....thats a very different thing.

Thanks for the correction - I've read a few horror stories about failures of the vacuum oil pump on these - I think I'll steer clear and get a OM642

 

[toteimerced]

The AdBlue system on pretty much all Mercs, aren’t very good and very expensive to repair, type of driving doesn’t make a difference, like it does with a dpf, some just delete the whole system, but be aware, it is illegal to alter an omission related item.

 

[Tonygw]

The Ad blue system gets a lot of bad press, but I know 3 owners with the system, two e class diesels and one c class. One e class is the V6 diesel OM642 and none have had any issues at all in the last 4 years or more.

It helps to ensure you buy good quality ad blue that's in date and stored properly. Buying from a petrol station or discount store will probably lead to issues.

 

[such01]

I've seen an 2016 S350d with a clean MOT history except the last one with this:



It's at a dealer, I have not asked then about it yet as just seen it.
Is this a new steering rack required -if so I imagine it would ne £££'s?

it's got 66k on the clock

 

[toteimerced]

This is just one problem AdBlue does and it doesn’t matter where you buy it, the AdBlue injector blocks.

 

[AMGeed]

I've seen an 2016 S350d with a clean MOT history except the last one with this:

View attachment 167769

It's at a dealer, I have not asked then about it yet as just seen it.
Is this a new steering rack required -if so I imagine it would ne £££'s?

it's got 66k on the clock

I'd be asking the dealer to replace the parts that appear in the advisory before committing to any purchase.

 

[Tonygw]

It's the inner track rods, not the complete steering rack. But needs fixing if you were going to buy. Not a major job though. Less than an hour's labour.

 

[such01]

This is just one problem AdBlue does and it doesn’t matter where you buy it, the AdBlue injector blocks. View attachment 167771View attachment 167772

Is there any way to prevent this blockage?

 

[toteimerced]

Take it off and clean it more often, maybe once a year, just to be on the safe side, but even then, it’s likely you’ll still get nox sensor and tank faults.

 

[Jobsworth]

Om654 and om656 suffer with camshaft and rocker wear problems, usually around 100,000 miles, sometimes less. I have done a few. Quite expensive job.

 

[OneForTheRoad]

Is there any way to prevent this blockage?

Use anti crystal formula in with the ad blue asap may help prevent build up if it's not already blocked up. As advised don't buy cheap dated ad blue from garage fronts , it prefers dark and warm places.

Along with Nox sensor revisions and software parameter updates , newer cars after 2017/18 on ad blue , should be seeing alot less trouble.

 

[such01]

Om654 and om656 suffer with camshaft and rocker wear problems, usually around 100,000 miles, sometimes less. I have done a few. Quite expensive job.

Thanks - I have seen a few 18 plate W222's OM656's with excess of 100K on the clock, in great nick/spec. Is there a way to check? Would more frequent oil changes prevent this wear? tx

 

[toteimerced]

More oil and proper spec oil changes will always help engine wear, but being used, it depends how often the oil changes have been done in the past, imho 10k is far too long between changes, 5k max for me.

 

[such01]

I'm looking at pushing the boat out and considering this:

Used Mercedes-Benz S-Class S350L d AMG Line for sale

Check out this Mercedes-Benz S-Class S350L d AMG Line for sale on PistonHeads. Get in touch for more information or to take a test drive today!

www.pistonheads.com

It has the OM656 on 70k, not checked history yet, but any pointers most welcome.
Thanks

 

[such01]

Or this-

Used Mercedes-Benz S-Class 3.0 S350d V6 AMG Line G-Tronic+ Euro 6 (s/s) 4dr for sale

Check out this Mercedes-Benz S-Class 3.0 S350d V6 AMG Line G-Tronic+ Euro 6 (s/s) 4dr for sale on PistonHeads. Get in touch for more information or to take a test drive today!

www.pistonheads.com

This one had some work done -


Should I be concerned these parts failed at low mileage? They have all been replaced
It's got good history too