There used to be a time when diesel Mercedes-Benz cars ran forever and were the last word in durability, reliability, and dependability. The 240D, 300D, and 300SD were slow, but they’d always get you where you needed to go, with rugged simplicity and overbuilt design. Unfortunately, those days are long gone, and some of the final diesel Benzes sold in America are absolute money pits thanks to the troublesome OM642 diesel engine. Here, allow me to walk you through the problems in today’s installment of “Achilles Heels.”
It feels cliched to condemn an engine, but I don’t find myself in that mindset often. I’m a little more lenient than others when it comes to reliability. After all, timing chain components are technically wear items, problems with known failure windows can be planned around, and any major flaw for which rectification can be safely bundled into routine maintenance is perfectly manageable. Hell, I drive an 18-year-old BMW and a 24-year-old Porsche, and I write about cars on the internet as a job, so I’m not exactly risk-averse. Still, the Mercedes-Benz OM642 diesel V6 is one engine I wouldn’t touch with a ten-foot pole.
So what is the OM642, and which vehicles came with it? Well, back in the mid-aughts, Mercedes-Benz wanted to replace its aging inline-six and inline-five diesel engines with one turbocharged diesel V6. The result was an undersquare (long stroke) all-aluminum 72-degree unit with a variable geometry turbocharger. You’ll find this engine in 2007 and newer E320 CDI and E350 BlueTec sedans, 2007 and newer R320 CDI, R350 BluTec, ML320 CDI, ML350 BluTec, and 2008 and newer GL320 CDI and GL350 BlueTec SUVs, 2012 to 2013 S350 BlueTec sedans, 2007 to 2008 Jeep Grand Cherokee diesels, the rare GLE350d and GLS350d SUVs, and a buttload of Sprinter vans.
With such widespread use, vehicles with the OM642 diesel engine can be commonly found on Craigslist, but they can also commonly be found clogging up bays in local repair shops. Let’s dive into some of the problems I’ve seen with this motor.
Dead Turbo Actuators
It’s not uncommon for the turbo part of this turbodiesel engine to become silent, with the variable geometry flaps inside the turbocharger failing to, erm, vary their geometry and instead resting in a collapsed “no boost” position. Should a no boost condition be caused by the externally-mounted vane actuator crapping out, Mercedes will tell you to buy another turbocharger at a cost of several grand as everything’s sold in one assembly.
There are aftermarket turbo actuators on the market that claim to be an easy fix, but from my experience, they’re badly made, rife with fitment issues, and lack acceptable longevity. However, assuming the turbocharger itself is fine, complete unit replacement isn’t the only decent option.
Unsurprisingly, there is a small cottage industry refurbishing these actuators, and it should have an OM642 back on the road for a few hundred dollars. Well, back on the road temporarily, at least. I’ve seen great success with these rebuilt actuators, but there’s still plenty that can keep an OM642 down.
Swirl Flap Failure
Like many modern diesel engines, the OM642 features swirl flaps in some of its intake manifold runners that promote air turbulence at low engine speeds, theoretically resulting in more thorough mixing of the direct injection fuel charge with the air entering each cylinder. As MS Motorservice, wholesaler for OE engine parts by the likes of Pierburg and TRW, explains:
Swirl flaps produce a swirl alongside the cylinder axle. They are used in diesel vehicles to improve the mixing of the fuel-air mixture at low engine speeds. For this purpose, the air is fed to each cylinder through two separate channels in the intake manifold. One of the two channels can be closed with a swirl flap. This creates a swirling of the fresh air. Better mixing reduces fuel consumption and pollutant emission. At higher engine speeds and torques, the swirl flap is opened to achieve a better filling level. The swirl flaps are also opened at starting of the engine and in overrun condition.
Unfortunately, these swirl flaps gunk-up and freeze in place thanks to carbon deposits made by the exhaust gas recirculation system in its mission to cut low-speed emissions, often taking out fragile swirl flap mechanism components like the flap “connecting rods.” Since they aren’t serviceable, replacement of at least one entire manifold is common, and simultaneous replacement of both intake manifolds (yes, each cylinder bank has a separate manifold) certainly isn’t out of the question.
Figure around $700 just for one intake manifold, and 6.1 hours of book labor to replace a single bank. If you aren’t handy with a wrench and blessed with plenty of spare time, intake manifold replacement easily results in a four-figure bill.
Oil Cooler Leaks In The Valley Of The Engine
Oh, and in the same vicinity of the gunked-up swirl flaps, you might find a pressurized oil leak caused by inferior oil cooler gaskets. Guess where these gaskets reside? That’s right, in the valley of the engine. This wouldn’t be so bad on many engines, but Mercedes-Benz crammed a whole lot of stuff in the way of the valley, from the aforementioned problematic intake manifolds to the turbocharger itself.
This issue is so common that Mercedes-Benz issued a technical service bulletin back in 2016 for this issue, and while the parts are cheap, replacement of the oil cooler seals calls for 12.3 hours of book time. Needless to say, this is a labor-intensive, multi-day job to do yourself, and typical European specialty shop labor rates make this repair cost a mint to farm out.
If you want to see the journey to the valley of an OM642, there’s a phenomenal thread on the Peach Parts forum that takes a DIY dive right in. It’s pretty easy to see why even the most experienced wrenchers might want to hire someone for this repair.
NOx Sensor Failure
Moving underneath the car, the OM642’s NOx sensors go bad all the time, and are some of the most common OM642 repairs I’ve quoted in a past life. Figure a parts cost of roughly $450 to $500 per NOx sensor, and these parts definitely need replacing as soon as they go wrong, as a failed NOx sensor can trigger the dreaded Mercedes 10-start countdown, an emissions safeguard which will only allow a driver to start their car ten further times before it’s immobilized.
Oh, and when I write immobilized, I mean immobilized. Exhaust the countdown, and the only way that vehicle’s making it to the dealership is on a tow truck. Besides, NOx sensors are vital emissions system components that sniff for harmful nitrogen oxide, and diesel gets a bad enough rep for the planet as it sits.
Main Bearing Failure
Oh, and just like certain high-performance BMW engines, earlier Mercedes-Benz OM642 engines may also suffer from engine bearing wear. In 2013, Mercedes-Benz put out a technical service bulletin for a ticking noise at idle and low engine speeds.
The common fix? In Mercedes-Benz’s words, “Replacement of bearing shells of 1st crankshaft main bearing.” While the repair can be done with the engine still in the car, failure to address this ticking noise can spell an early demise for the engine.
Looking around on car-part.com, an online salvage yard marketplace used by many independent shops for second-hand parts, a good used replacement engine goes for anywhere from $6,500 to $8,500, not including installation. Considering many OM642-engined Mercedes-Benz products have depreciated to that level, catastrophic engine damage would make many OM642 diesels uneconomical to repair.
If you’ve been considering a V6 diesel Mercedes-Benz, just go with a naturally-aspirated gasoline-powered V6 or V8 model from the 2009 model year or newer and save yourself some heartache. Potential fuel savings with the diesel can easily be swallowed up by engine repairs, to the point where you could’ve had a V8. Sure, the OM642 is smooth and torquey and efficient when it works, but unless you want to put your mechanic’s kid through college, I’d recommend other options for diesel-powered vehicles if you’re hellbent on an oil-burner. The E70 BMW X5 35d is a much better option than an ML350 BlueTec, and although the Porsche Cayenne Diesel, Audi Q7 TDI, and Volkswagen Touareg V6 TDI have their foibles, I saw far fewer of those three models combined booked in for unscheduled repairs than diesel MLs alone.
(Photo credits: Mercedes-Benz, Jeep, Mhobsonjr – Own work, CC BY-SA 4.0, eBay, Amazon, Peach Parts, Sprinter Forum, Benzworld, Mercedes Benz Owners)
Support our mission of championing car culture by becoming an Official Autopian Member.
-
Here’s What A ‘Conductor Plate’ Is And Why It Kills So Many Mercedes Vehicles
-
The 2008 Dodge Viper’s V10 Engine Was The First To Ever Use This Camshaft Technology
-
How ‘Indirect Tire Pressure Monitoring Systems’ Work And Why We Should Celebrate Their Return
-
How Parking Under A Tree Can Kill A First-Gen Porsche Boxster
-
I Bet You Don’t Know The What The First Car Crash Tested By The NHTSA Was
Got a hot tip? Send it to us here. Or check out the stories on our homepage.
The OM642 is an incredible engine and here’s why. In the UK its put in most heavy sprinter NHS Emergency ambulances and they clock up 500.000 miles easy before being sold off with very little going wrong. They are also hammered and driven hard from cold yet don’t fail .This engine has been known to go well over one million miles no problem. I own one in a E Class and was also a ambulance medic so know this engine well. My car has done 160.000 miles and its been faultless, just a new turbo 10 years ago. Also, the article talks about issues you can deal with yourself if you are handy, the swirl flap issue is very easy to fix with a resistor placed into connector. The oil cooler gaskets are the only big thing that can go, but most were upgraded. If you buy a car with one of these engines and its been well looked after and serviced I cant think of a better engine to get, that’s why the British government chose to have them placed in emergency vehicles that work very hard. I can see why some warranty companies wont like the engine because if its neglected and poorly looked after you will get high bills, but that’s to be expected. If you find a good one, buy it ! they are powerful and a joy !
a friend’s 350 blutec went kablooey 30k on the odo. he was very thankful to have bought a CPO car.
My husband purchased a CPO 2012 E350 Bluetec with around 20K miles on it from the local MB dealer. It came with a pretty generous CPO warranty, and we also purchased an extended warranty as well. The car was great. Not quick, but fast. No diesel clatter. Super quiet and comfy inside. Routinely would get 35-40 mpg on road trips with the cruise set around 85 mph.
Under warranty we had the entire oil cooler replaced, twice. The turbo replaced as well. Once it got close to 150K, (and out of warranty), things started to go south quickly. Check engine light came on. Replaced turbo again. Oil cooler again. Clogged NOx filter. Still never solved the issues. It started to become a money pit and we got rid of it to not soil the memories of a great car up to that point.
Yet Mercedes sells dieseled powered vehicles every year in USA since 2013. Don’t buy Blutec powered any car.
Which diesel Mercedes was final in USA?
Wow. What an eye opener. I was looking at Sprinters. And the fans say the v6 is a better cause real 4×4 with low range. 2023 awd. And new 4 cylinder diesel. I was learning towards the pre 2023. Now I’m inclined just to run. Had already planned on looking at aTransit today. I’ve had 2 Flexi, love the 3.5 ecoboost. Which if I remember right has it’s own problems. Seems like the diesel durability is over. I don’t know if the4 cylinder is all new or has been used in other applications. Tommy at FLT liked it’s performance. Some motors are more problematic than others. And some are more $ to remedy. And due to the durability (?) and other benefits (?) of design and function, diesels seem to always cost more to fix. The new chevy gas 4 cylinder turbo in the trucks (and other applications? I’m not sure) seems so far to have the benefits of turbo (high torque at low rpm) without the downsides. I think I read in part that’s due to it’s having incorporate some diesel design features.
Has this engine in a Grand Cherokee, all of the above happened to mine, when the oil cooler started to leak, it went down the road. The guy who bought said he could fix it. Put a bad taste in my mouth, a long with all the other Jeep issues that occured. Back to Chevy Diesels, have a couple 6.5s and have minimal issues, and when they do occur, easy and cheap fix.
The ones in america are not made in Germany, in Europe we are more lucky
I was wrong, they are all made in Germany and are the same 🙂 sorry.
You didn’t even mention the injector blow-by issue, which produces lots of black gunk around the injectors that’s a bear to clean off. And then there’s the time I went to replace the fuel filter and the &$%&^$%& hose clamps didn’t secure the hoses to the new filter correctly, which I discovered when I went to back into my garage and wondered what all that fluid in the street was – the day before a big trip…
Still, I had a 2008 ML320CDI that I bought at 133K miles and proceeded to put 60K more on. Loved that truck, traded it for a 2015 ML250 Bluetec. If Mercedes would sell me a diesel today, I’d rush right out and buy it, even though I’d probably take a big bath on my 2022 GLC300…
Not in the US.
Thanks for the great article on this somewhat niche subject Thomas!
I’ve come close to buying a Benz with this engine more than once… I figured my 20+ years as a VW TDI owner had prepped me for the task. Whenever I’d see a M-class or R-class diesel, I’d feel envious, even though quick googles reveal that their real-life MPGs aren’t really that great… nothing like what older (A4 and earlier) VW TDIs achieve (40 MPG auto/50 MPG manual). Still, I owned an (unreliable) early oughts Benz, and aside from the myriad reliability issues, it was a pleasant car to sit in and to drive (when it ran w/o a dash full of warning lights) so the idea of a small SUV (by modern standards) or even that sleek/weird minivan with a diesel engine has been tempting.
After reading your article, I’m relieved that I never bought one, and probably never will. I’ve also come very close to buying an OLD (pre-80s) diesel Benz, even though they have their own issues (HVAC, vacuum lines, etc…)… still haven’t ruled them out entirely though. 😉
W124s and old were built to a standard, not a price point.
Good news, the BMW M57 and N57 diesels have nearly the same issues.
Swirl flaps fail, EGR systems fail, the DEF systems frequently have issues, the DPFs fail, the NOX sensors are just as expensive as on the Mercedes. The emissions components put a diesel BMW into lockdown almost the same exact way, and if it gets locked down you get one “unlock” if you’re using the BMW dealer software (ISTA) for 50 miles, which is supposed to be enough to fix and test it. Otherwise the entire DME bricks itself.
That’s just the emissions stuff. Beyond that, the glow plugs like to snap when you’re trying to remove them. The high pressure fuel pumps fail and cost an arm and a leg to replace. The timing chains like to stretch/skip and it’s quite easy to screw up the chain timing if you replace the high-pressure fuel pump without the correct special tool.
On the N57 you get the bonus round of the timing chains being on the back of the engine, so you’re either pulling the motor or dropping the transmission and working on the timing chain in the transmission tunnel.
Of course you’ve also got the typical BMW oil leaks from the oil pan gasket and valve cover gasket, except now they’re much more difficult to do and leave you covered in nasty black goo the entire time.
The M57 also has harmonic balancer issues where the rubber between the two layers separate and leave you without any working belt-driven accessories, aka no water pump, no power steering, no alternator, no AC.
The charge pipes also like to blow up, especially if you tune the engine for more power, though I suppose that’s a general BMW turbo engine thing and not a diesel-specific one.
Save yourself the grief and just buy a gas engined BMW/Mercedes… at least you’ll be able to find people to work on it and the book times/parts are generally more reasonable on the gas engines.
Now I know why my brother was so keen to find a 2006 or older Sprinter
Edit to add: “Swirl Flap” makes me giggle
You read swirlie too?
But they rust so bad.
THey have more rust after 10 years than other cars after 50.
I’m pretty sure you could create an ongoing series called “Here’s why you shouldn’t buy a Mercedes xxxx” and never run out of topics.
Or “here’s why you shouldn’t buy a diesel XXX”
The sound of the 7.3l PowerStroke gives me wings, but that’s also a quasi-personal connection. That’s the only one I’d even think of owning, and either way my lifestyle does not require diesel anything.
The worst diesel I’ve ever owned was a 7.3 Powerstroke.
Ouch! I heard they have…finicky sensors or something? What about them is so bad?
I’ve heard the 6.0 is decent when bulletproofed but that the subsequent 6.4l was basically the worst–not even bulletproof-able. Or something.
You heard right on the later Powerstrokes. I wouldn’t own any of them.
My 7.3 had $$$$ injector problems, ate batteries and oil pumps, hated cold temps even with a block heater, etc. By the time I gave up on it, going out to start it each morning was a 50-50 proposition.
I spent enough on it that I could have rebuilt a gas engine from the crank up, and of course it still had issues when I sold it. Contrary to its reputation, this all happened with ~120,000 on it. Luckily the reputation is so powerful that I was able to sell it to the next sucker for only a small loss.
It’s funny, people seem to absolutely adore this engine, interesting to know it’s so problematic. I was under the impression the love for it was due to reliability. I know the 6.0 PSD is a nightmare, but I thought the 7.3 was a safe bet.
I see a number of beat to hell 90’s 7.3l f-250/350s in my area, they owners seem so proud of them. I imagine they really just bought a 7.3 that happened to have a beat down truck wrapped around it.
Honestly, I kinda just hate diesels across the board thanks to the diesel-bro crowd.
I have no doubt it can be reliable, as can some other diesel engines, the issue with me is always the price to keep it reliable.
A Toyota V6 or 350 Chevy can go for 300,000 miles with minimal running costs.
A 7.3 Powerstroke, VW TDI, or Cummins 12V can also get to 300,000+, what no one tells you is how much it costs to do so.
Right, plus the fact that they cost at least $1/gallon more to fuel.
My company had an F350 with the 6.0. That entire truck was cursed. It was put on its side by an improperly loaded trailer that started wagging on the highway. It broke off a chunk of one of the pistons, but still managed to run another 400 miles before it could be diagnosed. After we retired it from hauling, it was the snowplow; it then developed an appetite for batteries and a warm garage. Then the transmission decided it wanted to play “choose your own adventure” and forget how to use a torque converter until it was warmed up. The last straw was when the engine would randomly add a burst of throttle; that last one was especially embarrassing in gas stations. “Who’s this a-hole trying to get me to hurry up?”
The truly based among us spring for the 6.9/7.3 International.
I miss the one my company had, but it had 320,000 miles on it and could barely do 0 to 60 in a minute when towing. In its younger years, it was quite strong, but the 4.10 rear end jut put too many high speed crank revolutions on it. Running 2800 RPM at 65 MPH was not what that engine wanted!
Especially old mechanical diesels are some of the most reliable and cheapest to run vehicles on the road.
International/Ford IDI 6.9/7.3
VW IDI and alh TDI
Chevy/Detroit 6.2/6.5
The old Mercedes diesels mentioned in the article
Those are just the ones common in the US.
I will just say my experience has not been for any diesel to be reliable or cheap to run, no matter its reputation.
I understand others have been luckier than me, but personally if every diesel engine disappeared from every vehicle smaller than a 1 ton duallie tomorrow I’d call that good news.
There’s just so few parts and so few failure modes on a mechanical diesel, it can’t not be reliable. The advantages that make a diesel the obvious choice for everything higher than a one ton pickups also apply, sometimes more so, to light vehicles, including small cars.
Just the principle of operation of a diesel is a very efficient one. Also, in many ways forced induction on a gasoline engine is stupid when you’re always going to be knock limited, and you could just build a forced induction diesel.
Doubt it. By this point you would spend tens of thousands of dollars fixing rust holes, broken hoses, seals…
I seem to have a bad habit of buying cars that would fit these articles nicely. I’ve had a Ford Triton 5.4 and all the cam phaser/oiling issues, I had a Mazda CX9 with the dreaded Ford (again) PTU that turns your 4wd into Fwd, BMW’s craptastic N62 trainwreck, MB’s ABC system, I have bad taste related to my desire for something fancy at a bargain.
However, there are so many duds out there from the Ford 3.5 Ecoboost with the water pump INSIDE of the crankcase (when they fail, they dump coolant into the oil and you get to buy a new engine) to GMs 1.4 turbos that crack because reasons. Audi’s E-tron (all models) with bad water jackets that piss into the electric motors and destroy them are interesting (there’s a reason they’re so cheap used). What else, the GM 6.2 AFM/DOD, Dodge 5.7 and it’s yummy cams, I presume this is a topic with great potential. I love reading about how these things work/fail.
Seems like it might be hard to publish these without pissing off the manufacturer. Might never get another press car.
What model/year with the 5.4l Triton? I know my family had a ’99 E-150 with that and we got it to 240,000 miles before it needed new “coil-on plugs”? (or something similar that’d presumably have involved mechanics needing to get into the doghouse and have been way too uneconomical at that point in its life.)
Also, this is merely conjecture, but I feel like deeply criticizing non-current models/engines is far less egregious?
I hate that the 5.4 is so suspect. There are a few otherwise nice Ford truck models I’d be interested in, but they all have that motor.
They’re supposed to have so many issues, but we quite like ours with 190k so far. We bought it at the recommendation of a family member who had over 300k on one before it finally blew its plugs out, and have run several others to impressive age with notably few issues.
I think I remember reading somewhere the that the ones with the 2 valve heads were okay, but the 3 valves were problematic. I always found it odd that the 5.4 was singled out, while (AFAIK) the 4.6 and 6.8 share the same basic architecture.
The 2 valve heads had only like 2 threads holding the spark plugs in and had blowout issues. The 3 valve heads fixed this issue but introduced several others, including poor quality spark plugs that broke off in the bore and cam phaser issues.
The 4.6 and the 6.2 Boss has different heads and never had the same issues. The bottom end and general architecture is in fact pretty much the same, which is why if anybody tells you a 5.4 has any issues with the bottom end they’re dumb.
Good to know, thanks for the info! When I was a kid I had a 94 Cougar with the 4.6L. It was a 2V that was rated around 190Hp or so. Not a powerhouse at all, I used to call it the gutless wonder, but it was SO SMOOTH. That’s actually one of my favorite cars I’ve ever owned, it was a phenomenal highway cruiser.
Hooray for the old MB tanks! I had a 300CD that had 385k when I traded it in for a 4-door. Not fast but a true tank.
I think MB still makes reliable diesels, altough one has to get one of the inline 4 “taxi” engines or older inline 5 or 6:s. However bigger problem is the car round the said engine, they tend to be more problematic and expensive to fix. Also like any german car, they do not do well with any neglet related to oil excanges or quality.
But still there’s plenty of very high mileage taxi here in Finland with MB diesels of recent years. Quick lookaround in the used car sales, and there’s quite lot of 500tkm range e-series 200d:s for sale (2015->).
They do. Sprinter was on sale every year in USA since 1995
“ Swirl flaps produce a swirl alongside the cylinder axle.”
That should be “axis”. The flap closes off one of the two inlet ports (just like on a mk1 MR2 from the eighties) so all the air goes in to the cylinder off centre and makes the air inside rotate, like a tornado. Because you’re halving the flow area you’re also doubling the velocity, so it spins much faster than two ports designed to promote swirl.
You can get the same effect by varying the lift of just one of the intake valves, but without the carbon build up on the moving parts or leak paths through the manifold for flap axles.
Variable valve lift applied asymmetrically would give you finer control over the flow velocity and give much more swirl at low loads.
If you don’t have variable valve tech already designed in to the head it’s much, much easier/cheaper to do it with a bolt-on manifold.
So it comes down to cost and planning.
Maybe I’m jaded from V10 TDI ownership, and so many of these issues seem like regular modern diesel things.. but the 10 count death spiral does seem like typical Germans Germaning… anecdotally, I know of a few people with this engine who have had zero issues in ~10 years, while I… own a VW. They all have had these since new or very low mileage, and maintain them very well, whereas I got my Treg at ~100k with many mysteries.. so. That ole gem hasn’t changed.
What I’m getting at here is there’s no bad thing as a bad dog, only bad owners.
The ten start countdown ensures customers can’t ignore an emissions failure. If there was no limit you’d just keep driving with a warning light on for years.
10 starts doesn’t seem like enough though. Even if you book it in to a dealer as soon as you get a fault you’re unlikely to get it booked in that week.
Depending on how you look at it, it’s more lenient than VW’s approach of 650mi for AdBlue faults. If that light comes on early into a road trip up/down the East coast, you’re boned.
In my truck it’s 500 miles, which means if it ever happens when I’m on a long camping trip I’m not getting home.
Yeah well as the person who paid money for the car I reserve the right to drive it, with or without a warning light, whenever I want. This is some serious big brother stuff
Dude German cars led the way when it came to automotive paternalism. Besides these “wtf” engineering decisions I keep seeing on car sites and Reddit, that’s largely why I will never touch them.
At this point I’m starting to think Mercedes just doesn’t have that great of engineering…
I feel like German cars used to be overengineered in a solid, tank like way, but now they’re overengineered in a “we can shave 2mm off this part” type of way.
They kind of still are engineered like tanks. WWII-era German tanks were over-engineered too. They were impressive when they worked, but they were complicated to make and to field fix. Many German tanks were abandoned due to issues that would have been an easy field fix on a Sherman. I once watched a doc on tank restoration, they showed the beautiful machining and precision fit of pieces on a Panzer, then showed the same parts on a Sherman. The Sherman looked like it had been “machined” with a hammer and anvil, the restorer noted that the Sherman had been engineered that way for quick assembly and for ease of service by farm boys used to working on tractors and such.
Germans never engineer things unless they overengineer them. They are all about getting it not just right, but obsessively right. They won’t use two parts where 27 will do the job a bit more elegantly.
This leads to my favorite part about working on Mercedes: sometimes, all you can do is put the wrench down, back up slowly, shake your head, and say “Germans. Go fig.”
I’ve got an 87 560SL that’s down because I haven’t figured out how to drain the gas tank to rebuild the fuel delivery assembly in the rear…
Seems the engineers who designed the machines I train service techs on all went to German engineering school… lots of over-engineered, complex, and expensive to repair subsystems and parts, too many special tools/jigs.
Fun fact…
Our Mercedes ML350 Bluetec was one of my favorite vehicles ever.
We did lease it though and moved onto a GLE550e plug-in hybrid which ended up disappointing. The torque of the the diesel was just amazing and very fuel efficient.
If anyone finds an oddly optioned Selenite Gray ML350 Bluetec, it is ours and I may buy it back. We got nearly every option on the interior (including the custom Designo options) but exterior was completely vanilla.
We need more of these articles on known monstrosity engines lurking out there. Everyone knows an N54 is going to be a PITA, not everyone knows this one or some of the others that pop up on justrolledintotheshop etc.
LR/Ford/PSA’s Lion V6 turbodiesel…
https://www.youtube.com/watch?v=v3moekbW6z8&vl=en
Seems a discussion about “Mercedes Deiselgate” aka the AEM program would be good to cover here. When completed, it came with $$$ and a new warranty that covered some of the items you listed.
But not the oil seals. Our 2012 642 made it to 110k on the original seals. Did the swirl flaps at the same time.
That mileage and torque tho…
Fun piece, although my suggestion might be to call these ‘Achilles’ Wheels’ as opposed to ‘Achilles’ Heels’, as this site is so enamored of puns.
Ouch. Not easy to read, Thomas, and that’s not a comment on your writing skills.
Was expecting a mention of EGR valve clogging, which seems to be a common occurrence on newer models. My VS30 lasted to about 30,000 miles before I swapped in an aftermarket EGR valve. Took an hour.
I’m hoping MB fixed the turbo actuator and swirl flap issues by 2019, but I might be whistling past the graveyard if MB can’t figure out an EGR valve.
I live in a mountainous area, and it’s not uncommon for me to wring it out to keep up with traffic, so here’s hoping the EGR valve is the only issue we face.
Not including turbo actuator, most of these problems are related to soot buildup. If your rev it out, or take long drives you’ll probably be fine. All modern diesels EGRs are failure prone. Just delete it and tune it out depending on jurisdiction you live in.
Hypothetically speaking, there are DPF- and DEF-delete services available that require a remapping of the ECU/ECM. Such a delete would be necessary to operate the vehicle in countries selling high-sulfur diesel, such as those in South America.
A.) The GTA2260vk does kinda suck, though a little zealous about actuator failures here. However if you’ve got the 265 hp version or about 700 bucks and can wait for shipping from Poland. Get that sweet GTB2260vk. Bolts right in. The TDI community often runs these babies up to 35+ psi. If you want to play with waterlines vklr will get you even higher, with lower egts.
B.) Nox sensor and swirl flap are both often cause because no one ever revs out the engine. Modern German diesels need to stretch their legs here and there, get that puppy hot. More so if you often take short trips.
C.) It’s diesel, if you ain’t leaking oil, you’re out of oil. Really should of gone straight six though.
D.) I’ve got nothing on the main bearings, only a problem on the early engines
In summary the OM642 is honestly pretty alright. I say this as a TDI man, who worships the ALH. It’s better than the honestly pretty bad 3.0. And M57 makes cool ass noises, but you have common injector and DPF failure, that puts it on par with the OM for me.
Interesting, in Eastern EU markets these are considered pretty good and solid engines.
In the EU-spec Chrysler 300C and Jeep Grand Cherokees these are fairly desirable as they get relatively good MPG.
Lots of people do a swirl delete on these.
Valley oil leaks are also not a huge deal, it’s just like you wrote, buried under a ton of other parts so it takes a long time. But not too hard to do as far as I know.
Compared to simple gas engines, yes, they can be a pain to maintain, but compared to other modern turbodiesels from a similar vintage, I’d say they are average.
I suspect the issue in the US with cost to own/repair is down to extremely low take rates vs Europe which has historically had much stronger diesel sales. Due to scarcity state side and overseas factories for parts, everything costs far more here, and finding an independent shop that has experience with them is much harder, so not only are parts costs way high, but so are labor hours due to a lack of experience.
German cars these days are like my John Deere tractor. High performance, low reliability, major complexity of design, and stunning parts prices.
And you need to jailbreak the ECU to work on it outside of a dealership.