[®ob]

The other day I posted and I thought my coolant temp sensor/wiring may have been on the fritz. It still could be - but one more symptom I'm seeing is that the coolant temp increases with RPM, and decreases with lower RPM.

Edit - should have searched more - looks like this is a thermostat issue.

 

[maagjr]

It is a fact that the more combustion (fuel) and gas gets into the engine as the RPMs increase the hotter it gets, then it gets circulated by the water pump into the radiators.
At low RPM the combustion is less thus les heat and then (if you are still long) the car gets hot by not enough heat being removed by convection into the engine and radiator
Hope this helps, some