2001 Polaris Sportsman 400-500 DUSE and H.O. Service Manual, Page 149Get this manual
COOLING SYSTEM TROUBLESHOOTING
Overheating
&&&&&&&&Low coolant level Air in cooling system Wrong type of coolant Faulty pressure cap or system leaks Restricted system (mud or debris in radiator fins or restriction to air flow, passages blocked in radiator, lines, pump, or water jacket) Lean mixture (restricted jets, vents, fuel pump or fuel valve) Fuel pump output weak Restricted radiator (internally or cooling fins) Water pump failure Cooling system restriction Cooling fan inoperative or turning too slowly (perform current draw test) Ignition timing misadjusted Low oil level Spark plug incorrect heat range Faulty hot light circuit Thermostat stuck closed or not opening completely