I have a Y62 Nissan Patrol with the VK56DE (320hp) engine, GCC spec. Recently, I installed headers, a high-flow exhaust, and a new intake. After these modifications, I took the vehicle for a full tune-up, including a dyno tune with an ECU flash.

I was experiencing overcooling issues and found that my thermostat was damaged. I replaced it with an OEM 82°C thermostat. However, after the replacement, the engine temperature at idle or in traffic now rises to 98°C (with ambient temperatures between 18-28°C). The fan never produces a roaring sound, but the temperature drops slightly after reaching 98°C. On the highway, the engine runs at 89-90°C.

I replaced the fan clutch, but it made no difference. My tuner believes these temperatures are too high and are causing performance loss. I would like to know the normal operating temperature range for the VK56DE engine. Additionally,considering patrol fan is ECU controlled, should the fan behave like a typical viscous fan, roaring at startup and locking up as the engine reaches operating temperature? Currently, I can easily turn the fan by hand, even when the engine is at operating temperature.

For reference, during a dune bashing session, engine temperatures stayed around 90-95°C. Any insights or recommendations would be greatly appreciated.