What causes white marks on pistons in a Komatsu PC200-5 6D95 engine with overheating issues?

[Nicholas Villa]

I'm having an overheating issue on my Komatsu PC200-5 with the 6D95 engine. We already checked the engine, adjusted the hydraulic pump load, and even replaced the engine with a spare, but the machine still runs hot. After removing the cylinder head, we found white marks/patterns on all 6 pistons and combustion chamber areas. Trying to figure out the real cause of the overheating before replacing more parts.

 

[Harvey Esteban]

Since the overheating stayed even after changing engines, it really sounds like something outside the engine itself is causing it.