So to look at the customer satisfaction input on the OM642 diesel motor and on this car in particular, (2014 ML350) it would seem it was Indestructable. Everyone seems to love it.
But coming on here there's all this talk of engine seizures, etc. The car we plan to buy in the morning seems literally NEW @ 144K miles. It sounds PERFECT. Ive never friven a used car that seemed so new. It seems amazing! But all this talk of the Bluetech being a lemon and seizing etc..... need I be worried?

 

OM642 is real workhorse in production for over 20 years, but read more about oil cooler seals.
When they fail, the 7 bucks seals cost over $2000 in labor to replace, what can hit your budget.
2014 US models were subject to Bluetec Settlement and AEM warranty, who might be still in effect.
Check the VIN on this site for the status.
https://bluetecupdate.mbusa.com/home

 

is there an easy way to see if they might be failing in this particular vehicle?

 

You'll see an oil leak underneath the suv, dropping down the bell housing. You can't miss it. It can be severe or very slowly dripping (mine was slowly dripping for the last 3-4 years). I just did mine on my 2013 ML350 Bluetec sitting at 350 000km. It still had the original orange oil cooler seals, so they were due.

If you want my opinion, the OM642 is a great engine if you're very meticulous about the maintenance. Mine runs like new at 350 000 km, so is the transmission. I change my oil (Pennzoil Euro LX 0W30 229.52 MB approved) every 10 000km. I do the transmission service (fluid change, filter change, don't do a flush!) and change all the fluids (coolant, transfer case oil, front/rear axle oil) every 100 000km. It's a very heavy suv and it eats tires and brakes quickly. The whole anti pollution system (SCR) of the OM642 is one its weakness. If you live where they don't do emission testing, I highly recommend doing a whole delete (EGR, Swirl flaps, Adblue, DPF). I recommend Malone tuning if you're going that route (I'm not affiliated with them by the way). Here's a link to my maintenance sheet if you're curious.

I don't recommend the suv if you're going to bring it to the dealership for every problem (you're in for an expensive ride!), if you only do short trips such as city driving or don't drive much every year, and if you can't delete because of emission laws in your area (because the adblue system will fail sooner or later and it's very expensive to fix, unless you can do the work yourself).

I recommend the suv if you can do basic maintenance and know your way around a wrench. If you're in an area that doesn't do emission testing, that's also a big plus since you can go the delete route.

Don't be shy to use this forum and ask questions. This website has been awesome and of huge help to me. There are countless threads about known problems and how to fix them.

Good luck.

 

Suppose later models of OM642 have seals improved, but it is time bomb.
Meaning if they were not replaced by the seller, you better put some money aside for the job.

 

Short trips will lead to an early end of the engine. It isn't a grocery getter, it is a marathon runner. Treat it as such, with 5K mile oil change intervals with the occasional engine flush treatment, and you'll be fine.

 

100% agree - was strongly advised by my friend who owns a shop and repairs all of our vehicles that these motors MUST be regularly run on the highway to insure a good burn cycle from the DPF system. He sees a ton of Sprinter vans with this powertrain and has in depth knowledge of them. Has repaired oil cooler seals more times that he cares to talk about, and has also done quite a few DPF "flushes" (a time consuming and messy affair).

I only bought one because it had the full recall done - basically all parts in the diesel exhaust system were replaced. The previous owner had also done the oil cooler seal job as well.