I had the 3.0 litre 603a turbo in my 1987 300D turbo and loved that motor. Surprisingly quick.
You'll probably want to avoid one with the number 17 head (but the engines are cheaper because of fear) but I think the problems (head cracking -?) only occur in about 5 - 10% on the #17 heads. Many last 300-500,000 miles.
This is from a MB sedan site but it lists the possible problems with MB diesels:
- OM603 ('87)
Head cracking/warping if overheated
~30s cool down, carbon build up
Trap oxidizer issue, MB recall
Vacuum pump check, is it noisy. Is it updated, external screws on cover.
Injection timer ramp, wear?
- OM602 ('90-'93)
Transmission, weak point (722.4)
Headgasket leak if not cooled down, 20-30s (or cracked head)
Vacuum pump in engine bay (is it noisy)
C/C failure, actuator replacement
If sitting for months, algae. Watch out
- OM606 (1995)
Glowplugs carbonned up, hard to remove
Blower motor regulator
Weeping fuel lines and o-ringsere is a 603a engine which the owner says is a 2.5 litre but it has been on CL for months now.
1984 W460 280GE Cabrio