why is coblat running hot

ALWAYS CHECK RADIATOR COLD,! Never open the system once it has reached operating temperature! Check that 1. Radiator flows freely (cold) 2. Water pump weep hole is not leaking indicates weak or failing pump 3. Thermostat may be stuck closed 4. Hose leak. How old is the coolant? Did you use proper coolant when replaced? GM COOLANT SHOULD NEVER BE MIXED WITH NON SPECIFIED COOLANTS AS IT HAS BEEN KNOWN TO GEL!! COOLANT should be changed according to manufacture specifications check with the parts dept of dealership as to type and duration of fluid! Auto parts store can also help BUT DO NOT ALLOW THEM TO SELL YOU A UNIVERSAL COOLANT youre asking for trouble if you mix !

What tells you it is hot? Gage? Can you use a heat sensor gun to find the hot and cold spots? Is the radiator cool yet the motor is hot? Thermostat may be stuck if that happens. How old are the hoses? They get old and may collapse and restrict the flow of coolant. easy way is to replace the sensor IF it reads hot, yet there is no indication from listening or noticing the engine is hot. In other posts, the wire running to the gage was fried. Make sure the wire from the sensor is good all the way to the gage. Is the overflow full when it gets hot? Is there enough coolant when the engine is cold before starting?

Where is sensor for coolant fan for a 2005 cobalt