So, this has happened a couple of times, but not every time I drive the jeep.

Temp is at ~200 while driving, no spikes no over heating, nothing. all the cooling system is pretty new. New hoses, radiator, pump, fresh coolant, oem t-stat.

But when I turn the key off after driving for a bit, the temp will jump into the red, but if I turn the key to to on but not start, the temp will go back to normal, I did that a few times, and each time it went back to normal.

is it a temp issue, or an electrical issue I'm dealing with? any ideas?

89 4.0l.

 

That's normal.

 

My 98 dose the same thing and it is normal for it to rise some. But mine has never risen into the red.

 

It rises to the red, but if I turn the key, normal temp is registered.

 

So wait. Does it only go into the red when the power is off? I think it's just the gauge cluster Turing off. If it goes away when you turn the power on I wouldn't worry about it. It's just the gauge turning off.

 

Engine temp does rise after shutting down, due to fluids/air no longer being circulated, but not that much.

 

Try a new temp sender.

 

it slowly climbs to red after I turn power off. I'm used to it jumping a tiny bit, after turning off, but not going to red. if I turn the key to on, but not turn the engine over, it goes right back to where it is supposed to be, and about 200 degrees, so I think it is the sensor

 

I would verify the temp with an I.R. temp gaugeaimed at the t-stat housing. If it's close to what your dash gauge is reading while running I wouldn't be to concerned about it.

 

The rise on the gauge reading, after it has no power when IGN is off, seems normal. The gauge movement just relaxes with no power to it, and comes back up with IGN power.