It is overheating because the fan is not working. The fan may have a Defective fan thermal relay, bad fan, blown fuse, or disconnected or loose wiring.
Low coolant, inoperative water pump, head gasket failure, inoperative radiator fan, etc.
A bad water pump or thermostat can cause an engine to overheat. A plugged (clogged) radiator or heater core may also cause an engine to overheat.
It will almost certainly cause your car to overheat, which can lead to costly damage if it cracks a head gasket! Put some water in your radiator!
it is possible your radiator is clogged
A faulty head gasket can cause a coolant loss which will cause an overheat. Exhaust getting into the water jacket will cause it to overheat very quickly. 5 minutes, 10 miles. With it cold, take the radiator cap off and start the car. Water should shoot out the radiator a couple of feet high.
Low coolant? Radiator plugged or restricted? Water pump not circulating coolant? Hoses collapsing? Thermostat not opening?
You have a blown head gasket.
No it is not. It could be a problem with the radiator, a radiator hose or a water pump. In any situation, it could cause the motor to overheat and damage it severely.
when the enjine was turnoff sometime and then open the radiator and fill it
In order of probablility: low coolant level, faulty thermostat, plugged radiator, damaged water pump, collapsing radiator hose.
Low coolant Bad radiator cap Dirty or plugged radiator Thermostat cooling fan not working Water pump Collapsing hoses
A lack of water in your cooling system will cause your 2002 Pontiac Sunfire to overheat. A malfunctioning thermostat can also cause it to overheat.