1998 C230 vs. 1997 E320
 

I am helping a guy look for a car. I have a 1998 C230 and have been trying to find him one since I know it and like it, and will be helping him fix it. However, there are not many around right now, but there are quite a few 1997 E320's around. My main question is about the engine. What are the issues there? How long can that engine go? I know the M111 can go forever but how aboiut the M104? Would it be better to look for a 1998 with the M112? There are'nt many of those around either.

I always like the C230 non-supercharged also, yeah you might have a time finding one, was only made, what, 96-98 I think? The Kompressor models aren't bad little cars, but I htought it is a nice docile car without it and don't have to worry about the extra stuff.
Any number of things can happen to the M104 if not properly taken care of, the same can be said for the M111 as well. There are known problems with earlier M104 SFI cars with the wiring harness on the engine but I believe my this time MB knew about it and had changed the wiring harness materiels.
They are kind of known for both oil leaks at the front cylinder head cover and also the head gasket.
Not sure which of these have the 722.6 trans. You do read a lot about these transmissions. I would not avoid one over the other due to the transmission, but just throwing it out there, the 98 probably is a 722.6, the earlier one might not, if you need to know I can find out for you.
The 98 I believe has the smartkey as well, which I kind of like over a blade key, can be a hassle if something goes wrong though.
If I had a choice I'd definitely do a C230 over a M104 C280, just my opinion. Again the non-Kompressor C230 would be really high on my list if I were going to get a MB. I worked in a dealership in this time and have never owned an MB, but this would be the one I would look for if I were looking.

Could be wrong, but I believe 1997 is the year when the 722.6 5 speed was first used.

I believe it was started with the V12s and V8s and went up from there, I am wondering if the M104 ever had a 722.6, except maybe in the 140 chassis? I have the info somewhere on what had the .6 and what didn't. Anyways I wouldn't consider it any problem at all, others might. I know it wasn't just based on a model year, you can't say it started across the board for all models, it was phased in.

m104 is a good engine,use common sense and lower the thermostat,90,000 trouble free miles,and yes change trans fluid ever 30,000 miles.
Some V6s have issues with balance shafts,and harmonic balancers falling off.

The M112 is a great engine IMO. The M104 you speak of has a 722.6. I don't like the M104 due to its,leaks, the m112 is probably your best bet... the engine can go as long as you maintain it right, at least for a substantial amount of mileage at least.

my 97 c230 was the best car I owned, and I shouldn't have sold it, in hindsight. 98 is the same but with the updated styling cues. They are trouble-free cars as long as they are well-maintained. Make sure the trans has had good service, and that all the suspension rubber has been replaced.