Good day, first I would like to profusely thank the Jaguarforums community. This site and its members have been an invaluable asset to me as a jag owner.
(Note to "Moderators" or Host, please move this post to proper location if need be, most appreciated)

Cooling fan works as intended when water is in the cooling system (coolant flush etc) . However, the fan will not work when proper coolant is in the system. (Prestone dex-cool 50/50 orange)

Car at hand: 2002 Jaguar s-type 3.0.

I had to replace the coolant expansion tank recently (crack on seem). Fan has not come on since (unless water is in system). Thought fan was dead until I did a simple coolant flush, and behold while system was filled with water the fan operated like normal. Finished flush, filled with coolant, bleed system etc. Fan no longer works.

Cylinder head temperature (CHT) sensor perhaps? Or this part :BWD/Intermotor Engine Coolant Temperature Sensor WT5158: Advance Auto Parts ?

I have not been able to diagnose this with JTIS

Any ideas are most appreciated.

 

Sounds like the coolant temp sensor. Probably has some sort of contaminate in it that is causing this. Also Make sure there is no air bubbles in the system.