The 606 is an awesome engine, better than the 603 in many ways....no head issues, much more power, better economy....etc. An all around more modern and robust engine. The main issues that it seems to have are fuel system/seals/o-rings related. The delivery valves on the Injection Pump leak eventually, and there are a lot of little o-rings in the fuel system that can get brittle and leak air/cause running issues. The motor itself is good. It also has the risk of stuck glow plugs in the head.....that is one of the other biggest issues.

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