The cooling system is closed, and unlike NASCAR there is no fail safe way for fluid to escape if it overheats. instead the pressure will force the fluid through the weakest point in the system. Usually where the hoses meet the radiator or the block are where you will first notice the gas escaping
clogged radiator or bad water pump
It could be the thermostat. Open up the radiator cap when it is hot and see if the water is flowing in the radiator. If it is not then it may be a thermostat.
try a radiator cap......or you have a head gasket leak.
check the heater core stopped up radiator
Not necessarily! Let it cool down then check the radiator water level and the water overflow reservoir tank. In a properly operating system the reservoir adds water as needed to the radiator when it cools down after you quit driving. #1. The radiator should be full of water and the reservoir tank should be 3/4 full of water. #2. At a certain temperature or with the "AC on" the radiator fan(s) should be sucking air over the radiator and cooling coils. So! Fill the radiator and the reservoir and when it overheats in idle see if the fans behind the radiator are operating.
Be sure the thermostat is not installed backwards.
Blown head gasket?
A hot water radiator heats a room by circulating hot water through a series of pipes inside the radiator. The hot water transfers its heat to the metal of the radiator, which then radiates warmth into the room through convection and radiation. This warms the air in the room and increases the overall temperature.
the radiator will spew hot water on you
it can..rain has NOTHING to do with your radiator or the thermostat
Thermostat regulator is malfunctioning, water pump pulley could be bad, gas bubble in radiator hose.
Low coolant, inoperative radiator fan, failed water pump, restricted radiator, head gasket failed, stuck thermostat.