240D rings, sleeves; switching engines 300D
 

I bought a 83 240D. It would run but needed an overhaul so we put new sleeves, pistons, rings, etc., had the head done, injector pump calibrated, etc. The car ran good for 2 hard months (odometer busted) but now is using about 2 quarts every 50 miles, lots of blow-by. We are going to pull it down and see what we did wrong. My machine shop put .003" clearance on piston, I knew better but let the machinist talk me into it. Any clues or helpful hints? This my first Benz.
Amazingly, I put 3 cans of Freeze-12 in the AC and eureka, cold air! It doesn't leak!
Anyway, of all the used diesel MB's I've seen around, the only problem I've seen is the sleeves and rings are worn out; the bottom end, the head, the entire 20-25 year old chasis is great (dry climate, it is amazing what all still works), but the rings and sleeves are shot. Is this common or my imagination? In my experience any other make engine, diesel or otherwise , usually something else thrashes before the rings and sleeves. It seems odd and would be a tragedy if this was the weakest part of the vehicle. I love the car more than I imagined, but I will be heart-broken if this is a common problem. Rumor has it a 123 chasis is running around Lubbock, TX with a 350 Chevrolet in it.
Also, I have found a 82 or 83 300D turbo 4 door sedan that was stolen and burned but engine is ok (it was still running and cool when the fire department put the fire out. Firewall back is toast). I am looking for a 300D car with a shot engine and found a 77 model. Should I keep looking for a newer chasis?

Sounds like excessive clearance to me.

I agree that .003 piston to cylinder is a little too much, but I don't think this is the cause of your problem. I expect that you have something dumb going on besides that.

I personally would delve into the four cylinder before putting a five in its place.

Good luck,

Was your mechanic looking at the shop manual when he worked on it? Or was he just using normal machining clearances ? Did he know the first bore is a different size from the others ? Did he measure and bore each sleeve to the Respective piston which was going into it ?
Oil usage can be valve stem seals... but excessive blowby is pretty much a rings deal...
Did you measure the oil usage starting from when you got it running again ?
If you were to put in a 5 cylinder I would sure suggest using a NON turbo....to keep some of the wonderful working room in the engine compartment..
Going from Lubbock to Anywhere :D your engine will turn over a couple of million times... and the point of most action is the rings and sleeves... so when looking at 25 year old cars what you are experiencing is not that the rings wear out faster than usual.. but that the rest of the car survives better .... You don't notice the rings and sleeves on those cars which have already been crushed :D