Air cooling uses air to carry away heat. It works best on engines exposed to a high airflow. Cooling fins make exposed surface area as large as possible, allowing more heat to radiate away.
A liquid cooling system uses coolant to remove excess heat from an engine. It also uses a heat-sensitive valve to control circulation to help an engine heat up and maintain its operating temperature.
Rotors in a rotary engine are cooled by oil from the lubricating system. Housings are water-cooled, with additives to protect its alloys. A pulley on the end of the eccentric shaft drives the water pump and fan.
