[gclark0024]

I have a 3.0L ranger that started running hot and boiling over. I changed the thermostat but that doesn't seem to help. Sometimes it will run hot and you can let it cool down then it may not run hot for days and then it happens again. Whats up?

 

[Yoyizit]

Particles intermittently clogging the cooling system?

 

[kchopper]

The easiest things to check would be: 1) Is the radiator fan working? and 2) Check the coolant level and strength

 

[Suzuki91vx800]

check rad cap is all I can think of,make sure all of your hoses are in good shape, maybe check the water pump, take drive belt off and wiggle pulley in all directions including in and out if there is any play replace the pump. did you put the stock temp rated thermostat in it when you replaced it and did you put it in right side up? im going to bet on the radiator cap and what kchopper said that covers 95% of the cooling system

 

[gclark0024]

The fan seems to be working and the coolant level is good.

 

[Yoyizit]

I'd run LED monitors to make sure the fan is not intermittent and monitor anything else electrical having to do with temperature. Next time it overheats you'll know if it is an electrical problem.
You have a better chance of finding this if you can induce the problem.