erratic temperature gauge.
Everything will be running fine with my truck and all of the sudden I'll notice the temperature gauge dives all the way down to the bottom. It'll bounce back up and down a bunch of times. Sometimes the "check gauge" light comes on and will stay on. when this happens i hear the engine sounds a lot different, like it's working harder. Sometimes the check engine light will go on also. After sitting for the night, though, when i fire up the next day it is fine.
This has happened sporatically for the past few months but lately it has been happening quite frequently(almost daily).
I was told air in the coolant system (my coolant level appears to be just fine) which could indicate engine problems or possibly electrical.
I don't have the $$ to just start replacing things. Wondered if anyone had any thoughts or where i should start. Thermostat, Coolant flush, ECoolant Temp sensor?