What was found
WHILE IN FLIGHT AN OILY FOUL ODOR WAS OBSERVED ON THE FLIGHT DECK. TURNED OFF PACK NR 2, ODOR WENT AWAY. DURING PREFLIGHT PACK NR 2 WAS RUN FROM THE APU BLEED, NO ODOR WAS OBSERVED. FOUND NR 2 PACK COALESCER BAG EXTREMELY DIRTY. REMOVED AND REPLACED COALESCER BAG IAW A300 M/M CH 21-51-16. OPERATED NR 2 PACK, NO SMELL NOTED 1 20D10-3.