What was found
FLT 4757 - DURING CRUISE FLIGHT FROM ATL TO DSM, CAPTAIN RECEIVED A HYDRAULIC 1 LOW PRESSURE CAUTION MESSAGE. AFTER COMPLYING WITH ABNORMAL PROCEDURES CAPTAIN DETERMINED A LOSS OF HYDRAULIC FLUID. AN EMERGENCY WAS DECLARED AND AIRCRAFT LANDED UNEVENTFULLY IN DSM. MAINTENANCE INSPECTED AND DISCOVERED A TOTAL LOSS OF HYDRAULIC QUANTITY AND PRESSURE. MAINTENANCE REMOVED AND REPLACED THE LEFT ENGINE DRIVEN HYDRAULIC PUMP DUE TO IT BEING RUN DRY. THE HYDRAULIC FLEX LINE WAS CHANGED AS A PRECAUTION. AFTER SERVICING THE HYDRAULIC SYSTEM MAINTENANCE INSPECTED THE LEFT FUEL TANK AREA AND FOUND A CRACK IN THE LINE AT FUEL PANEL 550DB. MAINTENANCE REPAIRED CRACK IN LINE. (M)