ok my jeep is a 99 4.0. 113k miles on it. a few months ago i installed a new radiator, water pump, factory 195 thermostat, thermostat housing, lower radiator hose, and thermostat housing temp sensor just for peace of mind during the summer. ran good, great. tonight it was about 30 dregees in chicago and after sitting in the jeep for about 45 min, the gauge started rading past 210, with the heat on!!!! so i plugged in my torque pro into the obd port and sure enough it was reading 213 degrees. with the heat off, it jumped to 226 degrees at which the electric fan kicked on for a few seconds. that brought the temp back to 216 degrees. i looked under the hood and the reservoir tank is fine, no overflowing, and there are no leaks anywhere. i dont think this is normal? any thoughts?

 

Were you sitting still when this happened?

 

yeah i was

 

Do you regularly sit idle for 45 minutes at the time?

 

Fan clutch is suspect.

 

how would the fan clutch do this if you dont mind me asking? is it some how not engaging or something?

 

http://auto.howstuffworks.com/cooling-system.htm

 

thank you