So the short story is this, my wife's Touareg died and we needed a car. she likes German SUV's so we picked up this nice looking "one owner" 2012 ML350 diesel (she drives 70 miles each way daily, all highway miles) in the MPLS MN area. All seems good, drives well, needs tires of course. Price was basically NADA value with 100K on it. She loves this thing right away.
So after I search everywhere in the car for the key for the locking wheel bolts I end up at the dealership where it had been purchased new (found a card and the sticker in the glove box). All good, they have a master set and can get the wheels off. The cut me a fair deal on new tires, alignment, oil change and did a wonderful inspection for me. They were actually very good and i am pretty happy with them and their service.
Now, i am a big DIY guy and used to work as a mechanic so lots of stuff doesn't bother me. Motors, transmissions, suspension etc I have done plenty of work and have lots of tools. I am pretty good at electrical stuff as well so i wasnt afraid of buying a diesel with 100K on it, especially a MB.
then the inspection comes back and the hammer gets dropped.
oil cooler leak, injector leaks, broken rear spring and a small coolant leak. Funny how clean that thing was on the lot (flipper lot) and just 2 days of driving all this stuff shows up. (As Is No Warranty, I knew that, but was assured the car was fully inspected and "one of the cleanest we have ever seen" The missing wheel key should have been a clue. The tires were so bad I wouldn't let my wife drive it, as the inspection I had done showed 1/32 on one tire-no biggie every vehicle i have ever bought used needed tires-OK new tires no big deal.
So over the next couple of days I researched the list and am confident that I can fix everything I know about, however the potential sludge issue has me concerned. Looking through the oil filler cap I cannot see how much crud there could be in there.
The quote for the repairs from the dealer was high but not unexpected. I can do the labor and buy a few more tools and the cost of the parts isnt too crazy, until I run into computer module related things then it looks like this could get crazy stupid expensive. I have a good basic OBD scanner but it looks like I might have to invest in that STAR and related items if I encounter problems.
next I found at least 1 busted motor mount and I suspect a bad CV joint right front. It doesn't make noise except when turning right and under some acceleration, again no biggie. This doesnt have the air suspension but again having to do the work on a 100K MB disappoints me.
First cold day here and the car wouldnt go into drive. Once the car warmed up it went into drive. Researched all the known issues, aux battery etc, all OK suspected the ISM. only other symptom was the low key battery warning. replaced those and all OK for a couple of day, then the low key battery warning came back along with the "wont go into drive" problem. after a bunch of stuff about trying to get the key to sync (keyless go) to see if something odd was up with the immobilizer stuff keeping it from going into gear I tried starting it with the key inserted rather than just in proximity and it goes right into gear. stopped the engine, put the push button in, get out, get in, brake on press start, low key battery alert comes up, car starts but wont go into gear. back to insert the key and it seems to work fine. Read dozens of related threads, not happy about the possibility of transmission control module and required programming to make that thing work if thats the root cause but i am leaning towards the AAM. issue happens with both keys. Seems to be fine in any temp using the key inserted though. seems to be fine if the temp is above -10 or so but i havent had it long enough to know if this is actually temp related or not. was thinking of some sort of antenna issue but without the more expensive scanner system it will be tough to sort this one out. Not a problem till it decides not to go into gear at all, then I will probably have a meltdown. Im not impressed with MB that they would have allowed a design that can immobilize this thing to the point where a dealer cant even get it into neutral with some sort of manual override? I get security but this is kind of crazy.

Anyway, I have already found some pretty good information on this forum and others that should help me address some of these problems but I sure wish I had done a lot more research into this OM642 engine and the problems other owners have experienced before I bought it, my bad. We were short on time and threw out the rules for a nice looking car. I guess we will see if this thing puts me into the trailer park by the time we get some good miles out of it.

I would like to say thank you to all the forum members that continually provide support to people like me who will end up asking for help with stuff. Without forums like this, Youtube, and other places we would be completely at the mercy of large corporations bent on getting as much money out of our pockets as possible. I dont know if Chrysler brought anything good to MB but I doubt it.