[MudMagnetYJ]

I would try your temperature sensor/sending unit as well. They're $10-25 for a decent one. It's in the thermostat housing, so it might be easier to replace it once the coolant is already out as you're doing the thermostat.

Don't forget to squeeze the upper radiator hose and get air out of the system. It will overheat your engine and ruin your coolant.

 

[harcosparky]

Do you watch it all the time, or only when you are slowing down?

I would think some fluctuation to be normal.

Gets up to 210 ..... then the thermostat opens and lets in cooler liquid ...... temp drops ...... thermostat closes ........ gets up to 210 ...... then the thermostat opens and lets in cooler liquid ...... temp drops ...... thermostat closes .... and the cycle continues.

I see this temp cycling in all of my properly operating vehicles.

I watched nay sons 4.0 XJ while it idled for temp to get up, and drop when thermostat opened. This is normal. One other thing that could induce a temp drop is turning on the heat.

In fact an old trick if you see it to begin overheat is CRANK UP THE HEAT ...... the heater doesn't do all that much to get rid of heat ...... but it sure can help.

 

[AMCJunkie]

Do you watch it all the time, or only when you are slowing down?

I would think some fluctuation to be normal.

Gets up to 210 ..... then the thermostat opens and lets in cooler liquid ...... temp drops ...... thermostat closes ........ gets up to 210 ...... then the thermostat opens and lets in cooler liquid ...... temp drops ...... thermostat closes .... and the cycle continues.

I see this temp cycling in all of my properly operating vehicles.

I watched nay sons 4.0 XJ while it idled for temp to get up, and drop when thermostat opened. This is normal. One other thing that could induce a temp drop is turning on the heat.

In fact an old trick if you see it to begin overheat is CRANK UP THE HEAT ...... the heater doesn't do all that much to get rid of heat ...... but it sure can help.

Never did it before to me, only happens when driving and foot is off gas.

When coming to a stop, it will lower then go back up to 210 if I sit long enough.

I do watch the gauge closely, always have. Slight movement always happened, but never came off that physical 210 marker, drive, stop, park etc. never in past.

 

[AMCJunkie]

Sorry for double post, can't edit...

When I said never came off, that is running of course, always drops when turned off so to my knowledge gauge always worked.

Figured I'd clear that up to avoid any potiential trolls lol

 

[Luckymac]

If you replace the temp sending unit, get an original from Jeep. About 4X the cost. No sense to spend anything for a sending unit that you can't trust.

Good Luck, L.M.