it has a cracked head
The above answer would be an extreme condition to cause this problem. Usually a car overheats because of either low coolant level or a stuck or bad thermostat.
Low coolant, inoperative radiator fans, stuck thermostat, failed water pump, restricted radiator, head/headgasket.
replace your radiator cap...
Can be the thermostat which is cheap to replace, or it might be the head gasket which is expensive.
A radiator may boil over in a minute due to low coolant levels, a malfunctioning thermostat, a clogged radiator, or a faulty water pump. When coolant cannot circulate properly or regulate the engine temperature, it can quickly lead to overheating and boiling over.
It could be low on water and stuff, fill it.
Engine overheated. Possible causes are: Thermostat stuck closed. Low of coolant. Defective radiator cap. Clogged radiator. Defective Water Pump.
Engine coolant temperature is cooled by the radiator, moved by a water pump and controlled by a thermostat. If there are troubles with any of those components the coolant will boil Also if the head gasket goes bad gasses from combustion inside the engine will get into the coolant and cause it to boil.
Stuck closed thermostat or a bad head gasket.
Thermal inkjet printer causes ink on print head to boil.
When the radiator cap is removed, the pressure inside the radiator is released suddenly, causing the water to boil explosively due to the rapid decrease in pressure. The water in the radiator is under pressure to raise its boiling point, and when that pressure is suddenly relieved, the water can boil and turn to steam very quickly, leading to an explosive release of steam and hot water.
you boil it
Try a new radiator cap.