What was found
(CAN) APPROX 30 MINS AFTER TAKE OFF, CREW NOTED LOSS OF OIL QTY IN NR 2 ENG & DID AN AIR TURNBACK. SEVERAL MINS LATER CREW NOTED FLUCTUATING OIL PRESSURE IN NR 2 ENG & CARRIED OUT A PRECAUTIONARY SHUTDOWN. MX ISOLATED LEAK TO AN AREA WHICH HAD BEEN DISTURBED BY MX THE PREVIOUS DAY DURING A B-CHECK. AT THAT TIME, COKING HAD BEEN NOTED ON OIL LINES INTERFACE AT REAR TURBINE FRAME & A GASKET REPLACED IN REAR BEARING HOUSING. INVEST IN THIS AREA FOUND TOP FITTING OF OIL SUPPLY LINE LOOSE BY 1 FLAT (60 DEGREES). B-NUT ON THIS TUBE IS RETAINED BY A PIN WHICH TENDS TO ADD DRAG TO TORQUE.