Higher Mileage ML550 Reliability?
 

I'm looking at purchasing a mint 2012 ML550 with 104k miles from a Mercedes dealership. The car appears to have been taken very good care of and has many service records.

Does anyone have a 550 with the M278 engine with 100k+ miles?

Any feedback on the M278 engine and related transmission over 100k miles is appreciated!


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Chris

I’m at 160k miles on my 2013 ML550. You didn’t specify the options it has (certain options bring their own problems).

For the M278, they seem pretty solid if serviced on time. Check records for replacement of fuel injectors, and installation of a check valve for the timing chain.

If the fuel injectors leak, it can get into the wiring harness and damage other electronics (in my case it was the ECU).

The check valve is minor, but seemed to be pretty consistent as there is a TSB for it. The symptom is a ticking / slapping noise when you restart the car about an hour after it’s been parked from a prior drive. Just roll the windows down and listen closely for any ticking noise when starting. The dealer installs a check valve to keep the timing chain from making the noise and doing any damage.

Check the wiring in the rear bumper for your Blind Spot Warning radars since I see this one has the Driver’s Assistance Package - my sensors failed due to corroded wiring at 145k mi after a rough NY winter. They cost about $2600 to replace everything in the back bumper if the radars fail. If they do fail it wreaks havoc with dashboard warnings and disables the rest of the distronic features (to include cruise control). I’d only be concerned if it was a car driven through states with road salt / chemicals.

As for the transmission, check the records to see if the transmission fluid was changed at the proper 39k mile intervals. If not, change it. Otherwise, they seem to do just fine.

The other issues I’ve run into are related to options for my specific car (Multi-Contour Seat Failure, Airmatic Strut Replacement for Knocking Noises, Valve Block for Active Curve Sway Bar etc).

I don’t regret mine for a moment - but the maintenance costs are not cheap. ML550s have a different sized brake rotor from all the other MLs (bigger than ML350, smaller than ML63). Gas mileage is obviously not amazing (I see about 16-17mpg on average). Windshields can be costly when they break ($1100-$1300 depending on your options). Distronic components are certainly not cheap, so make sure they all work.

Also, the 265/45R20 wheel size is not common - I’ve always had to order them in, and the selection isn’t great. I’ve stuck with Pirelli, but they seem to average around $180-240 per tire. These W166s love to eat tires - just a heavy vehicle.

Otherwise, get a PPI done and address the issues found and hopefully enjoy a great car.

Good luck.

When you say they eat tires, what sort of mileage do you get.

My rear tires have less than 7,000 miles on them and they are about shot.

I had the car wheel aligned and hopefully it will improve tire life.

7000 miles?! I don't see how that could be possible. I'm using Michelin Continentals during the Summer. I have about 50-60 000km on them and they're soon done. I agree with OldMerc when he says that the ML eats through tires. I would also add rotors. Mine seems to eat them faster than a 7 year old going through ice cream. I have the ML350 BT, but I suppose the weight is about as near as the 550.

Tire and brake wear is strongly influenced by driving style. Hard cornering, stomping on the brakes and strong acceleration whether on dry or slippery pavement all make a big difference in component life.

I got 50k miles from Eagle LS2s, and 100k miles on factory brakes with a late model Touareg.

Looking like my W166 will achieve around 35k miles with Conti Cross Contacts. Not sure yet about pads and rotors. I'm at 20k miles now.

These are solid if you keep up on them. Airmatic I would say is the biggest issue.

Almost all my miles are Freeway miles or carting my Wife's 2 dogs and then it's drive like a Nanna as they get carsick.

The car has a gentle life so the tire wear surprised me as I have W163 and it does well on tires (and I drive it much harder than the W166 and tow car trailers with it) and my Wife's SLK55 does really well on tires.

Brakes seem to last forever on it.

I guess just see how it goes after the alignment.

I see about 30-35k on Pirelli Scorpion Verde AS Plus tires with a 740 treadwear rating. A set of Michelin Tour HPs on my 19in set made it about 30k as well. Most of my driving is interstate bound. I think it’s the weight as they wear pretty evenly - I take them off once they get too noisy, so I could probably get another 5k out of them.

I used to see 50-70k with other vehicles.

My first set of Pirelli run flats failed at 18k after they wore to the point of belts breaking loose - first and last time making that mistake.

Rotors have lasted about 70-75k without much drama.

Airmatic hasn’t been a problem to be honest - it’s never failed on me. But I replace things based on mileage. I just replaced the rear bags and struts at 150k to the tune of $3k - the bags were alright, but showed wear marks. The fronts are next.

59,954 miles onML350 original brakes and pads. replaced OEM tires at 41,653 Oh, but I'm a old man.

Well, I hate to tell you this story. I purchased the same vehicle 5 months ago with 82000 miles , A Virginia car that was in excellent condition. Except for a minimal engine vibration which occurred not long after the purchase. Then the CEL came on that identified low compression in cylinder 3 and 4. The end of the story is two failed exhaust valves leading to a valve job on the passenger head to the tune of $4300.00. The second item was unusual. The radiator had a minor leak requiring the radiator to be replaced for $850.00.

My advise. Take it to a COMPETENT service garage and have it checked thoroughly. If you want to go the distance you can have a compression test done for around $250.00. That will give you a good understanding of a number of engine components.

The car rides excellent and a good sound system. First and last Mercedes.

Good luck

Let me add that the CARFAX looked outstanding having all the service work done by a Mercedes dealership. The thing to remember is the CARFAX only shows was has been reported by a participating garage. It is not the bible. Buyer beware is an appropriate statement.

Tires: I have a 2007 GL450, which weighs about the same. I am on my 2nd set of Michelin Primacy LTX tires, which transform the vehicle. Very quiet and stable, good life of 40-50k. When the Air Springs start going bad, the tires are ruined in short order. Do not try to delay replacement of the air springs
Tires: Pt2: My wife's GLC300 has the Pirelli Verde Run-Flats, which went 45k miles, then howled like crazy, because worn. Put on new ones- now all ok. I had such good luck with Michelin's on the GL450, I stayed with them on her.
Air Springs: I have 180k miles on my GL450 and the Air Springs went out at about 110k miles. Will throw all sorts of code and odd driving behavior. Also, will burn out the Air Springs compressor. When one goes, replace them all- then good for another 110-110k miles.
M278: Technically fabulous, but the Engine Number should be higher than [ 278 928 301 28000 ] An improved cylinder coating was used after that #; possible other updates (timing chain check valve?)

M278- cost can blow up big-time, if the right stuff goes bad; I am talking $15-25k. These are highly-stressed, very high-output engines, state of the art designs. But I am jumpy about the M278 vs. my current M273, which seems bullet proof; uses no oil at 180k miles; only a water pump and thermostat. I am looking at a used Gl550 with 106k miles, but I will pay a dealer to run all sorts of tests, before going forward at about $160-250.