2004-2005 660 Yamaha Rhino Factory Service Manual, Page 239Get this manual
OIL COOLER
CHECKING THE OIL COOLER 1Check: oil cooler Obstruction CleanApply compressed air to the rear of the oil coolerDamage Repair or replace the oil coolerNOTE: Straighten any flattened fins with thin, flathead screwdriver2Check: oil hoses Cracksdamage Replace