Radiator

What it does

The radiator is a grid of thin aluminum tubes filled with coolant, mounted at the front of the car where it gets maximum airflow. Hot coolant from the engine flows in one side, air blows through the fins, and the coolant exits the other side 20–40°F cooler. It's the same principle as the cooling fins on a motorcycle engine — surface area exposed to air removes heat. When the radiator leaks (cracked plastic end tank, corroded tube), or becomes clogged with rust and deposits (from years of neglected coolant), it can't shed enough heat — and the engine overheats.