I'd like to share my overheating story with you. About one month ago, on a camping trip, my 2005 Tacoma overheated on the way home. It seems that we got low on Coolant. Okay, so I drain it, (about one gallon low), flush it, and refill it.
Three days later, it overheated. I couldn't find any leaks. I put in a new thermostat and added about one gallon of coolant.
Three days later, it overheated. I went to Grease monkey for an oil change etc... Oil looked fine, coolant looked fine.
Overheated again - Took it to the local auto repair shop - they couldn't find anything wrong with it; looked for leaks, ran it for 1 hour, took it for a drive.. nothing. cost, $25
Took it to the Toyota Dealer - they found everything wrong with it - failed radiator cap, dirty radiator, leaking water pump, exhaust in the coolant... Price? $2,900 to repair everything!!!! Nope.
Took it to Charlies Toyota repair - They diagnosed a dirty radiator. Took it out and removed Cottonwood cotton, hair, and all sorts of dirty nasty shit from the outside of the radiator.... $160... and...
IT WORKS!!! I've run it for one week, up to the mountains twice, in 95° heat, with AC, and it works fine. no coolant lost, no overheating.
Whew! I was freaking out. Sometimes it can be something very simple.