Cooling problem with Jeep Cherokke

Vehicle is a 2001 Cherokke, 4.0

Problem: I start the vehicle and bring it up to operating temperature (gauge
reads between 190/210). Heat in vehicle works fine.

On two occasions I was driving along when a warning chime sounded and the "Check
Gauges" light came on (I had been driving for roughly a half hour...outside
temperature was in the 20's). I looked at the temperature gauge and it had shot
up all the way into the red zone (260). The first time it happened I pulled
over, shut the engine off, and checked under the hood. I didn't notice or feel
anything that would indicate the engine over heating... no excessive heat,
steam, odor, or "pinging". I restarted the vehicle and the gauge dropped back to
210.

A couple of days later, it happened again; only this time the "check gauges"
light turned off and the gauge dropped back to 210 before I had a chance to pull
over (fortunately this time it happened I was about 100' from my driveway).
Again, no observable symptoms of excessive overheating.

Once I was able to check things more closely, I noticed that the upper and lower
radiator hoses were warm to the touch, and there was no pressure and very little
coolant in it. The radiator and cap were just barely warm.

There's no sign of any fluid leaks or lost coolant. The level in the expansion
tank hasn't gone up or down. The electric fan has kicked in a couple of times,
but the gauge was still in the safe zone (about 230).

I replaced the thermostat (195), and it's still running the same way... engine
warms up, heat is fine, but radiator, upper and lower hoses are barely warm.

What could be the problem here? Weak water pump? Clogged or blocked hoses and/or
radiator?

FWIW, the outside temperatures here have been in the low/mid twenties.

 

Yes, all of the above, and more (cooling fans, fan relay, fan temp sensor)
may be problems, but based on your description, I'd suspect a faulty coolant
temperature sensor. Easy to replace and fairly cheap too.

Bob