if you must have a diesel get the land rover diesel.

If you must have a Mercedes diesel. Get yours cpo elw or extend the factory warranty mb elw as long as you can and be prepared for extended trips to the Mercedes service lane.

Get acquainted withr your service advisor.

The air air suspension will become the least of your worries.
Adblue heater failures.
Dpf failires
adblue tank failires.l cracking and crystallization
oil cooler failures
timjng chain stretch.
Timing chainguides failures. And tensioner.
sludge.

And if if you plan on keeping it. 5k miles oil changes. Especially if it is a grocery and city runner. The diesel hates trips under 15 mi.

I agree with the doom and gloom statement, the forum attracts most of the negatives with these vehicles. Mine is over 60,000 with an ELW to 75,000 miles. Urea Tank, Rear Brakes, and New Tires only issues.
I am very happy with the ride and build quality.

I sold my R350cdi at 190k miles, zero engine issue, just had to change the airmatic at 90k (2.600€). As a GP i only do lots of very short distances.

My GL350 Bluetec has 50k miles, I am not too worried, here in EU 95% of MB SUVs are diesel, nobody would want something else.

There might be an issue with US diesel and/or climate that I am not aware of though...

JN

Ah, I forgot : on top of doing very short distances, I only change oil when requested, every 20k.

If the forum info was correct, my bluetec should have melted at 30k.

I don’t want to generalise, but it seems like most of the forum contributors refer to some article posted by a mysterious ex-MB mechanic, rather than own expérience. Am I correct ?

I thought Mercedes diesels can run forever with maintenance. You really got me scared to not buy this car which has been great so far. Is this particular engine junk? Seems like ours runs great and we just do the factory service schedule.

what is the issues with the ad blue system? Seems like it may become a hassle. My wife doesn’t want a car that is hassle and constantly breaking down even if covered by warranty. Is this engine really that bad? We’ve had it 2.5 years with 36k miles and engine is perfect.

why is it that the engine hates trips under 15 miles? all these issues at what mileages should they Ben expected? You make this thing seems like a piece of junk.

The adbkue system has multiple known issues.
First in cold weather and if the tank is not completely full, it is prone to cracking.
Then if it is not drained and flushed every once in a while it will crystallise.
Then if you eventually just keep driving normally, the adbkue heater will fail. And if you ignore it, the car will eventually do a countdown timer of starts left.

Most first owners never have an issue with as as they usually get rid of the car before 50k miles. It is around 40k and after that a lot of issues come to light.
And it's not hhe owners fault, a lot of it is mercedes not informing owners how to maintain the cars properly.

This car hates short trips. To get the emissions system running, the car superheats the engine to get everything up to spec, dumping extra diesel in preparation. It superheats the turbo, (plus the turbo is oil cooled) and everything around it rapidly. Everything from seals, to engine mounts fail from the heat.
Hydraulic heat sinkaterial engine mounts melt from the heat, the seals that often are mentioned do not hold the temperature. Etc etc. Extreme heat, as one can imagine, is horrible for the oil too. Leading inevitably to other issues with the oil (sludge) etc.

But that isn't the only issue. Often fuel, due to the leaking seals, will find its way into the oil. The first sign of this is often a warning saying the oil has been over filled and owners frantically going to the dealer asking them to take some out. What the dealer won't tell you after they've taken out some oil to appease you is that the cause for the high oil level is that diesel has made its way into the oil and effectively ruined the lubrication properties of the oil.

Also, when one drives short trips this compounds a lot of the issues. The engine works super hard to prep everything to emissions ready, preparing itself at some point to perform a dpf regeneration (burning off all the collected soot in the diesel particulate filter). Short trips at low speeds inhibits the car from performing this, yet the car will constantly try to put itself in ready mode to perform it.
What causes the car to finally perform a dpf regen? Driving at highway speeds for more than 15 mjnutws is the shared trick. Driving around town at low speeds for quick runs just doesn't cause it to regen.
So what you end up having is a dpf filter that is chocked full of soot...so full of soot that a proper burn is not even attainable anymore leading to replacement.
But....a .replacement is easier said than done. Some owners have been waiting a long time for a dpf filter. But the om642 engine is pretty popular, so waiting as long as some members with the 250 diesel om651 engine will probably not happen.

There are a lot of issues. I could go on even more. But the best thing to do is read the post by a former merc mechanic called Stephens service.
http://www.stephensservice.com/blog/

It is lengthy, but well worth the read. It wil detail most of the issues and only then can you decide if the long term issues are worth the pleasure of the car.

That being said, I do adore diesels. I have torn around the nurburgring in some pretty awesome diesels. Once in a bmw 435d and a bunch of times in a m550d wagon (my unicorn). 380hp and a butt load of torque is awesome. Getting great mileage whilst doing it is awe-inspiring.

If you do decide to keep your diesel, take all advice given with a grain of salt. Some owners will be bitter with the frustration their diesel have given them. Some owners will defend their diesel to the very end. Other 's are just trying to provide a voice of reason.
But do get an extended warranty, preferably the mb elw or the mb cpo elw. It will save you from much pain. The constant issues will be easier to bare from a glc loaner, or an e300 if you're lucky.

Whichever way you choose. Whether you switch to a gas model, buy a new diesel from another brand or stick it out with the missus
Wishing you the best of luck!

P.s. Us owners of mb diesels are really sol because these issues don't really happen on eu models.

you are incorrect.

In our extended family, there are 4-5 om642 engines in Europe, the most recent being a 2016 s350 l, the oldest being a 2010 e350

None of these have ever seen issues comparable to the us om642 engines. A reason why I, and the rest my siblings and parents here avoid the bluetec engine here in the US.

An uncle just sold a 2011 s350 with 227k km and it had no major issues, only regular 20k km oil changes.

The e350 is at 300k i think.

The issues seen in the us are not replicated elsewhere, as I've mentioned before on many other threads. Thus its not helpful to contribute information saying your diesel runs perfect; when in fact the diesels in the US market were crippled from the start.
It gives a misleading picture when others are trying to give a clearer picture to the og op to make an informed decision.

Thanks and that's my rant.