TM 9-2320-361-20 1-19. POWER SYSTEMS OPERATION (Contd) f. Cooling System Operation. The cooling system removes excess heat from the engine. Major components of the cooling system are: ENGINE OIL COOLER - Removes excess heat from engine oil. TEMPERATURE GAGE SENDING UNIT - Detects temperature of engine coolant and sends an electrical signal to temperature gage on instrument panel. THERMOSTAT - Shuts off coolant flow to radiator until temperature reaches 180°F (82°C). Coolant is then allowed to flow to the radiator through the upper radiator hose. RADIATOR FILLER CAP - When removed, filler neck serves as filling point for cooling system. When installed, cap allows cooling system to pressurize. RADIATOR - Directs coolant through a series of fins or baffles so outside air can remove excess heat from coolant. UPPER RADIATOR HOSE - Directs coolant from engine block to radiator when thermostat opens. FAN - Pulls outside air through radiator to remove excess heat from coolant. WATER PUMP - Circulates coolant through cooling system. LOWER RADIATOR HOSE - Directs coolant from radiator back to engine block. 1-54