What was found
CDG - FLT 23 - AFTER TAKEOFF FROM CDG, CREW NOTED THE LEFT HYDRAULIC QUANTITY DECREASING TO ZERO, AND THE LEFT SYSTEM QUANTITY AND PRESSURE LIGHTS ILLUMINATING. CRWE ALSO RECEIVED THE EICAS MESSAGES L HYD QTY AND L HYD SYS PRESS. FLIGHT RETURNED TO CGD AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND A SEAL RUPTURED IN THE LEFT EDP PRESSURE AND CASE DRAIN FILTER MODULE ASSEMBLY. MODULE WAS REPLACED. THE VENDOR REPORTED THAT A PRESSURE SURGE OCCURED WHICH DESTROYED THE FILTER AND COCKED THE FILTER HOUSING, DAMAGING BOTH THE FILTER HOUSING AND CASE THREADS, RESULTING IN THE LEAK. (M)