What was found
DURING CRUISE FLIGHT, OIL COOLER LIGHT ILLUMINATED. EMERGENCY PROCEDURES CARRIED OUT, SWITCHING THE FAN TO THE SECONDARY BLEED AIR FAN. OIL TEMP REMAINED IN THE GREEN AND THE AIRCRAFT LANDED SAFELY AT BASE. UPON ARRIVAL, IT WAS DETERMINED THAT A LEAK IN THE TUBE TO THE HYDRAULIC FAN ON THE OIL COOLER HAD DRAINED THE FLUID IN THE UTILITY SYSTEM. THERE IS A TECHNICAL BULLETIN, TB 214ST-89-99, TO REPLACE THE FAN MOTOR AND HARD LINES WITH A MEW MOTOR AND FLEX LINES TO ADDRESS THE ISSUE.