• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Erratic Temp Gauge on 98 XJ


NAXJA Forum User
Yesterday on my way home from a trip to Utah my temp gauge randomly started reading about 140 for running temp. Once in awhile it will spike up to 210 for a minute or two and then drop back to 140 or so. It is a 195 degree t-stat. After it has been reading 140 for awhile I turn the heater on and it is definitely not very warm which makes me think it's a malfunctioning t-stat. Once I see it spike up to 210 I turn the heater on and it is warm. Gotta be the t-stat right? I purchased a new 195 t-stat but haven't installed it yet.
I almost never recommend installing random parts with no diagnostics, but thermostats are cheap, easy to install, and the symptoms are what one might expect for a failed thermostat. When my 00 had those symptoms, the thermostat had broken apart.
On my 98 its usually the connection on the sensor is corroded. un-plug>plug back up good to go.
Had this same thing happen today on my 99 XJ. Plenty of coolant so I tried disconnecting the sensor at the tstat housing and re-mating, that seemed to fix the low reading.
So I topped with coolant but it was only a tad bit low. I unplugged the coolant temp sensor and inspected, no corrosion. I was about to replace the thermostat but now everything seems fine. Air bubble? I'm keeping the thermostat/gasket and tools to change it out with me in the Jeep for awhile just to be safe.

Thanks for the responses.
Wire plug corrosion does happen.

The Cherokee open cooling system is self bleeding, after a few start/run/stop cycles of driving any air bubbles are purged.