Idiot Temperature gauge.

Hallo Jeepers.
My temperature gauge is acting like an idiot.
On the highway it gives 210 F and then there is a drop to 190F.
After 5 min it starts al over again.
What would you do first on a very cold day? I have do do it outside in the snow!
#1 To look for an air bubble?
#2 A bad sender? (56027012). Easy fix and to combine with #1.
#3 A bad gauge? Shit.
#4 Bad wires or contacts?
#5 Bad thermostat?? The changes in temp. are too quick?

p.s. If it is #3 maybe a aux gauge will do the job much better. The tread of the sender is 1/8"x 27 NPTF. Most senders of the aux gauges do they have the same size?
any solutions or experiences?

'92 XJ

Dude,that's normal.The fluctuation is the thermostat opening and closing.

At extended idle my 90 4.0 will get to an indicated 210, highway driving indicated 195.

I haven't noticed it making any large fluctuations like you describe.

Mine holds pretty steady at 210. Maybe your thermostat is sticking a little. Fluctuating between 190 and 210 shouldn't hurt anything though.

Well, I hope that frank36 is telling, is right. But I didn't noticed before.
Maybe it is by the cold weather, that the coolant is fluctuating.
At least ,I bought a new sender. (13 euro's, Crown).
When it is not working, I bye a gauge for the dash with a other sender.
But where can I put that new sender? Any ideas?

whenever i install a new thermostat, i see a noticable opening and closing of the thermostat by looking at the temp gauge.

your "problem" seems normal to me.

Hallo. I renewed the sender and I had for a short time a second temp gauge with an other sender.
You were right guys! No change in behaviour, it is normal.
The Jeep is only running too cold. The thermostat is doing his job.
The new radiator and the hoodvents make the coolant too cold with this cold weather.
Maybe a radiator screen/cover will work.
I am waiting for the summer. :woohoo:


'92 XJ

Maybe take a tip from the big diesel trucks--make some kind of variable grill cover for extreme weather.

Just use some cardboard in front of half of your rad, when its really cold.