2004 John Deer Buck Utility ATV 500, 500EX and 500EXT Service Manual, Page 33Get this manual
The following charts are provided to help in diagnosing the probable source of troublesIt should be used as guidelineThis section pertains to engine mechanical components onlySome related problems can come from other systems such as ignition system, fuel system etcand have an impact on the engineEnsure to check the other systems prior to concluding that the engine is in fault Check condition of impeller located on the water pump shaftImpeller wings broken andor impeller thread is damaged? ReplaceGo to next stepCheck coolant drain screw on water pump housing MAG side (marked "Drain")Copper ring on drain screw leaks? Retighten screw andor replace copper gasket ringGo to next step
Refill (refer to "Cooling System")Go to next step
Check cylinder head andor cylinder base gasketWorn out gasket(s) is (are) causing water leakage? Replace gasket(s) and refill with coolant and oil (refer to "CoolingLubrication System" and "Specifications section")