Had a slight themostat housing leak last week so I replaced the housing with the metal one,housing came from Jag w/ thermostat and all. Install went fine but the next time the car was run the twin cooling fans come on running on high and I mean high speed.Gauge indicates normal range,coolant is flowing,no air pockets. So next I replaced the cross over pipe that had fan temp sensor in it,again from Jag,and problem persists. When they come on I can turn on heater for a minute or two and they go off.Turn heater off and they come back on high.I took water outlet temp with laser and it read 165 *F,the water return read 145*F.No reason for them to even be running. The fans cycle thru low,medium and high as the engine warms up so I do not believe it is the fan control mod. I do not know the range of the thermostat as it came from Jag with the housing so I did not question.Also replaced the water pump 4 or 5 months ago with no issues.

car has 62K miles,no other issues.

At wits end.

Andy

You should check for fault codes with an OBDII reader. Use one that can also monitor engine parameters, and see what temperatures are reported.

Then post the codes and temperatures back here for advise.

Thanks White, I see your point, I will check that out.

Thanks again