Engine 3L

I'll tell you about the motor. Diesel aspirated 2.8. I passed around 400.000km. Over the past 10 years, only 60.000km. There was a replacement for pistons and head swam as a consequence of overheating (stupidly flew cooling hose and antifreeze quietly washed away). Also changing nozzle. After all this is only run 50.000km. The engine is considered, ultra-millionaire. The only trouble the last couple of years has become a worse start up in winter. Previously, quietly plant in -30, -15 are now below already hard. ? Maybe somebody will read this and tell me what can be the reason?