Yesterday I took my jeep for a little joy ride around my pasture (5 acre, sandy).As I was driving around I noticed that my temp gauge staying in the middle like it has for the past 2 years.As I was heading up a very small hill and all of a sudden I heard a jet engine noise coming from my engine compartment and looked at my temp gauge.The needle was slowing moving toward the hot.I slowed down and then stop, and turned on my heater inside the jeep. After about 2 mins, the temp gauge needle started to go back down.I then parked the jeep, waiting for about 10 mins, checked all the fluids (which was okay), radiator was cool enough to touch.Then in about 30 mins I drove it again (to town) and back and the temp gauge stayed in the middle.So what would cause the needle to go crazy?I've taken many rides in my pasture before (even on very hot days down here in SC) and I've never seen this.Any suggestions?

 

If your coolant is not quite full enough you can get an air pocket in the head right where the temp sensor is. Steam which is hotter than the liquid surrounds the sensor and makes it read high, but your radiator is not all that hot.

As for the "jet engine noise", that could have been your fan. Do you have an electric fan? The increasing temp reading would cause it to kick on high (if it's a 2 speed fan).

Or, another possibility is that the noise was from your belt or a pulley. Maybe you have a bearing going bad and something locked up while the engine was presumedly running slow in the field, but highway driving has enough RPM to keep it turning.

 

Mine did the same thing

Water pump from rock auto saved my weekend lol.

Water pump was weeping out and never noticed it till it ran hot