Odd erratic engine temps

[TomPrestin]

in the stock car all that matter is the cheap stock thermal gauge is not flying or land H.... that is all there is stock.

here is mine
rock solid even with back full of bricks and springs collapsed on a hot day.  no matter what solid, once at normal temp.

if say the hot normal engine shows 180f or what is normal for your car. IDK
and no rhyme  nor reason temps fluctuate say parked. wildly surging temps?.
what can cause this?
the o-ring behind the water pump sucking air  , or that silly steel pipe same rusty end.? front? making o-ring can't seal even new ring, rust pits happen here. this old sure.
or the clutch fan went nuts? or belt slip to it (is pump belt)
the thermostat tries to prevent all this  but do know that if air bubbles land on either temp sensor (wet) ect or coolant main (or your whatever it is) the sensor will lie its ass off.
due to fact that  bubbles are air and not water, so it fails.
I know you burped it, but if the pump sucks air it fills with air in seconds. and the sensor is up high, very high.