What was found
(CAN) THE CREW HAD SMOKE IN THE COCKPIT. THEY NOTICED THAT THE LT ENGINE OIL PRESSURE HAD DROPPED. THEY TURNED OFF THE LT BLEED VALVE WHICH CLEARED THE SMOKE THEN THEY SHUT DOWN THE ENGINE AFTER THEY LANDED. I FOUND A LARGE AMOUNT OF OIL ON THE ENGINE'S TAIL CONE. THE OIL WAS COMING FROM THE NR 4 AND 5 SUMP VENT TUBE. THIS ENGINE HAS HAD THE NR 4 AND 5 CARBON SEALS REPLACED TWICE IN THE LAST YEAR DUE TO OIL LEAKING ON THE VENT TUBE AND HAVING HIGH SUMP PRESSURES.