Temp gauge problem

[dusty88]

So my 97 xjs check engine light came on today so I hooked the obdll sensor to it and it told me the coolant level was low. It was about half full so I topped it off. The check engine light is still on and now the temp gauge will go from 100 to 260 in under a minute and then go back down and so on. Anyone know what would cause this

[4.3LXJ]

Air in the system most likely, or a stuck thermostat

[Brasscatz]

Yep, what Steve said.

[dusty88]

Thanks. I guess I'll flush it tomorrow and see if that does the trick

[OldFaurt]

So my 97 xjs check engine light came on today so I hooked the obdll sensor to it and it told me the coolant level was low. It was about half full so I topped it off. The check engine light is still on and now the temp gauge will go from 100 to 260 in under a minute and then go back down and so on. Anyone know what would cause this
On my 1992, I found the upper radiator hose was acting like an air trap.
With the hose routed below the AC lines, it traps the air right where the thermostat housing meets the upper hose.
I re-routed the hose above the AC lines and the bubble dissipated.
The erratic temp gauge has been tame for about 3 weeks.

Worked for me, your your mileage may very!:rolleye0012: