What was found
FLIGHT 5981, STL TO IAH. WHILE CLIMBING THROUGH FL190, THE CREW NOTICED THE OIL PRESSURE FOR E1 DECREASING BELOW 50 PSI. THE QUANTITY WAS THEN CHECKED AND IT INDICATED 2 QUARTS OF OIL. THE ENGINE WAS SHUTDOWN PER QRH PROCEDURES AND THE AIRCRAFT RETURNED TO STL AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE ENGINE AND FOUND THE SHAFT O-RING ON THE NR 3 GENERATOR WAS BROKEN AND ALLOWING OIL TO LEAK OUT. THE O-RING WAS REPLACED ACCORDING TO AMM 24-31-01 AND THE ENGINE WAS OPS AND LEAK CHECKED GOOD.