Hmm.. if XF uses only one fan and fan runs fine when AC is on, I guess its not fan motor. Water temp gauges working fine, so I'm eliminating coolant temp sensor. I have checked coolant reservoir, it was in between max and min, I am not seeing any coolant leaking evidence on under tray..

One mark by u mean "orange" line in my picture? it has never gone that high, usually sits at "blue" line no matter how long I've driven the car or jus idling in parking lot for hours. Today it went up to "purple" line, and went down to "blue" as I turn on ac.

Please check attached photo and confirm.

Hmmmmmmm its getting very very stressful now. I can drive with ac on all time to make sure preventing overheat,, but it cant be a solution.. helpppppppp