Stuck thermostat, faulty fan clutch, faulty water pump, restricted air flow, low on coolant, missing/damaged fan shroud, restricted coolant flow from a plugged radiator core to name a few.
Common causes include low coolant, inoperative radiator fan, radiator restriction.
A plastic radiator will crack under extreme over heat conditions for example a defective thermostat or bad cylinder head gasket will cause a cooling system to over pressurise and rupture.
Expansion of the water inside due to heat causes the system to be pressurised.
Conduction is the heat transfer process that warms your hand when placed over a radiator. The radiator transfers heat to your hand through direct contact, as the molecules of your hand gain kinetic energy from the warm radiator surface.
Either you have low coolant, defective cooling system (bad radiator) or a blown head gasket (or all of the above).
Maybe your cooling/heat system is all plugged up with radiator deposits. You could try flushing the radiator and see if it helps.
Causes of over heating: insufficient coolant; antifreeze/water mixture not correct; thermostat stuck in closed position; faulty water pump; clogged/dirty radiator; leaks in the system.
The heat transfer that warms your hand over a radiator is primarily convection. As the air surrounding the radiator is heated, it rises, carrying heat to other surfaces such as your hand. Additionally, some heat transfer may also occur through radiation, as the hot radiator emits infrared radiation that can be absorbed by your hand.
You can feel heat from a radiator through conduction, where direct contact with the hot radiator causes heat to transfer from the radiator to your body. You can also feel heat through convection, where the hot air near the radiator rises, creating a current that carries heat to you.
You have a blocked radiator.
Low coolant, radiator restriction.Low coolant, radiator restriction.
Too much heat.