what could be the culprit...
the temp guage will work fine. but sometimes when the truck is started up within minutes the guage will go to "overheating". the truck isnt though, ive checked all that stuff under the hood. so a sensor has to be bad... any idea what sensor and where?

thanks in advance

 

it might be facing up, coming somewhere out of the water jacket
it should look like a electric plug with two or three wires coming out of it