[speeder]

I think that the correct nomenclature for the car you are referring to is "SD350". The 3.5 version of the OM603 engine has a bad rep, as stated above. They punched the displacement out too far and the pistons oval the cylinders and bend rods. The beginning symptoms are oil consumption and a rough idle due to loss of compression in one or more cylinders.

The 3.5 OM603 is possibly the worst engine ever foisted on the public by MB and the only bad diesel they ever made. I have a 3.0 OM603 in my 1987 300SDL, those are not affected by the bottom-end issues of the 3.5 and have good reputation. My car has 186k miles and the drivetrain is in close to brand new condition with zero blow-by or oil consumption. It runs clean and quiet with great torque and fuel economy, (about 30 mpg highway in a long-wheelbase w126 body).

I've seen people drop a 3.0 in the later 3.5 cars and make a great car, but that's more trouble than it's worth unless you have a spare 3.0 OM603 laying around. I do happen to have an extra and am on the lookout for a car to put it in.