What was found
EN ROUTE, PILOT REPORTED THAT RIGHT HYDRAULIC PRESSURE LOW ANNUNCIATOR ILLUMINATED. PILOT CHECKED HYDRAULIC PRESSURE, IT WAS AT 1900 PSI. AFTER ABOUT A MINUTE ANNUNCIATOR WENT OUT. CAME ON INTERMITTENTLY & FINALLY STAYED ON. LEFT HYDRAULIC PRESSURE LOW ANNUNCIATOR STARTED FLASHING, FOLLOWED BY HYDRAULIC PRESSURE FLUCTUATING. BOTH ANNUNCIATORS ILLUMINATED AND PRESSURE DROPPED TO ZERO. DIVERTED. DECLARED AN EMERGENCY AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED AND FOUND LT FLAP DOWN HYDRAULIC LINE IN WHEEL WELL AREA, CRACKED. MAINTENANCE REMOVED AND REPLACED THE HYDRAULIC LINE, HYDRAULIC SYSTEM LEAK CHECKED OK AND AIRCRAFT RETURNED TO SERVICE.