2003 chevy tracker 2.0 4wd
Why does it overheat when im driving but not when its
Overheating at highway speeds are caused by a stuck thermostat, a restricted radiator, or a kinked hose. More than likely you will need a mechanic’s help in finding and fixing the overheating issue.
Thermostat sounds likely, but dont forget about the radiator cap. If it gets weak it will allow the coolant to leak out of the system and the system temp will rise while under load. A quick test for low coolant while driving, turn your heater/defroster on with the temp control on high. If the air is cold but the engine is showing "hot" you need coolant ASAP. Oh, and have your coolant tested for the proper mix percentage also. Too much water is a bad thing.