M-B diesels, oil leaks. Buyer beware

We have had five M-B over the last decade, all but one bought new. The last is a 2011 ML350 Blutec that now has 50k on it. Has ran very well with good fuel economy. Servicing it is expensive but not unexpected, about the same as our Cayenne.

However, after our car was afflicted with a peculiar failure I did a little research and learned it is not only common, but virtually certain to happen to M-B diesels using the 3.0L turbo engine of the last four or five years.

One day it started leaking oil. Nasty black, garage-staining oil-fuel mix. One drop, then more, then every time we stopped a few drips.

Turns out there is an oil cooler situated in the Vee of the engine toward the firewall. A poorly-designed o-ring style gasket fails and allows the Vee and back of the engine to be coated in oil. Service manager said if left untreated it can also ruin the RMS but I am doubtful, but who knows.

It is a $10 part and the original design will fail. 50-80k mileage is the time frame as I understand it. Replacement requires removal of the injection system and the turbo assembly. Luckily ours was covered under warranty, if not to replace this cheap part requires $1700 labor in our case. It is a difficult job to do without special tools to remove the turbo as I understand it. Hopefully the new Viton version hold up better.

There has not been a recall for this. Perhaps M-B is hoping most cars make it out of warranty before it happens. maybe I was lucky mine failed early.

Just a nasty surprise for anyone considering a CPO M-B diesel.

 

Yes, if you did everything by the book at the dealer for Bluetec I think it would rival normal maintenance on a few exotic-ish sports cars.

I learned to drain and refill the AdBlue tank myself (very easy) using VW/Audi fluid and a $5 fluid transfer pump that is only used for DEF. The VW stuff made to the exact same ISO standard is $13 for 2-1/2 gallons while M-B charged $32/gallon. M-B filling up the tank is about $230, with a drain and refill every 20k is about $450. Instead it is $45 and an hour of my time in the garage.

I really hope the change to Viton for the seal cures the problem, I trust M-B engineers to correct this error. After my wife is done with the car I will probably inherit it for my commute and barring any major calamity it could have 250k on it before I sell. Forking out $1700 because of a stupid, unservicable design would burn me for sure.

For some reason if I had say a 308 or 360 that needed a $2k repair it wouldn't bother me as much as it does on a new car supposedly engineered to be the near perfection, according to the hype.

 

If you drive (I put 30k/year commuting) or don't plan to trade every three years, leasing doesn't make sense.

My '09 Accord will turn 150k in a couple of weeks. We will see how long it lasts. 250k? 300k? It is basically worthless with those high mileages, may as well drive it until something expensive breaks and dump it.

 

New fun tonight on the ML350 that inspired this thread. Wife had a CEL a couple of days ago. Took it to Auto Zone and the code was P20BE, which is the heater inside the DEF tank. Apparently this is a very common failure, although why it failed when the weather it is still warm is strange.

Anyway, looking around the filler cap area there looks to be a connecter just under the sheet metal, I thought what the heck maybe it is loose. With -very- light pressure, the damn pump nipple just shears off in two and starts squirting DEF. This thing is so flimsy, roughly the size of a coffee stir stick about 5mm diameter, I guarantee a person would easily break it off trying to remove the tank.

So checking tonight the pump assembly is about $600, not that surprised although the design is incredibly poor. And the heater, what would you guess? How about a nice round $1000 for this stupid thing for the part. The entire tank with heater and pump is only $1400, which is what the dealer usually does, just replace the entire tank assembly for about $1700 after adding labor.

So in the morning it will be a call to the dealer to see if I can get a loaner on short notice and if this heater failures falls under the EPA emissions warranty. Car is out of normal warranty but not federal mandated warranty period for emissions. I would guess the AdBlue system is part of emissions but we will see.

Changing the tank is perhaps a 2 hour job and could be done myself. If this is entirely on my nickel that is what will happen. Online for $1250.

And the rest of the car? Frustrating penny-pinching and poor engineering in places. Example: tail light bulbs. These cars use a bus system and the bulb is in a holder, no wire to the bulb holder, UNTIL the holder and bus ground erodes a few years into the life of the car and then the owner must pay for a $25 "kit" which consists of a new holder and separate ground wire, basically the owners finish assembly of the car. Did one of those myself, would hate to think what a dealer would charge in labor. Two more are also acting flaky. Good news after doing three, there are only four more to do.

We have had five Mercedes in the last 11 years: 2003 ML500 (used), 2004 C230 (new) 2005 C320 (new), 2008 C350 (new), and this 2011 ML350 Bluetec (bought new, 63,000 miles). This car was the most expensive by a large measure and we have had more problems with it than all the other combined. My ML500 at 129,000 miles worked perfectly, not sure I trust this thing to drive across the state at half that mileage.

I could tell a decrease in quality from our '05 to '08, and this one is starting to be very frustrating to own. Will probably be our last Mercedes if it is up to me, my wife could buy another one but if she does she is on her own with it. No tundra-warranty for her on another one.

 

The car is used through the week on a 15 minute commute (about 5 miles) each way. Weekends it is usually an hour (50 miles) minimum from startup. In the past few months we have reverted to taking my '09 Accord (175k miles!) because it has never let me down while we do not trust the ML. A sad statement regarding the quality of this car.

Car has been maintained by the book, 63000 miles so far.

I agree this will be my last and only M-B diesel, if not my last Mercedes. We had good luck with the other ones. Looking back the "best" one was probably my '03 ML500 or my wife's '05 C320 Sport Sedan.

Forgot one last one, its last time on the flatbed to the dealer. Started the car in July, every fan on the car going full blast, no A/C, car had no power, and it said the outside temp was 187F. I immediately thought temperature sensor on the front of the car. Turns out it was the climate control computer, which then messed up the temperature sensor, which then made the engine think it was that hot outside and effectively shut the car down. Not exactly the most robust design in the world when a problem in the air conditioning prevents the rest of the car from working. The dealer fixed this with no cost to us out of warranty to their credit, probably the only reason I am paying them to fix this latest problem now.

 

please tell me this is a joke.