I have the YD25 model. I was getting a slightly rough idle and after a while( bout a month) noticed water/coolant coming out of the coolant reservoir overflow when engine was hot.
Carried it to my mechanic and after the engine warmed up air bubbles were also coming out of the radiator. This was a sign of engine loosing compression.
When he took off the head, there were cracks at some points. Head gasket was fine. He also said there can be cracks inside of the head that are not in plain site. This is why he advised to buy a brand new head instead of using a used one ( got this from N&M, had to wait about 3 months).
He also said that it was most likely due to material failure since i got no overheating problems.
To note, this happened to me around 185xxx km. Also dont use any cheap coolant. Spend your money and buy the original coolant for your engine to preserve your parts.
Dont completely fill the overflow, dont know why nissan didnt put a max mark.
Still 'breaking eeen' engine 1000 km more lol