What was found
INTERMITTENT ENGINE OIL ODOR IN CABIN/COCKPIT DURING CRUISE/DESCENT FROM VENTS. WENT AWAY AFTER BLEED SOURCE SWAPPED TO APU DURING DESCENT (FLIGHT 6068). TROUBLESHOT PER FIM 79-20-01 FOR ODORS IN INTERIOR OF THE ACFT. PERFORMED OPS CHECK OF BOTH PACKS IAW AMM 21-51-10 WITH ALL 3 BLEED SOURCES AT ALL POWER SETTINGS. AT NO POINT UNDER ANY CONFIGURATION WAS THERE A FUEL OR AN OIL ODOR NOTED IN FLT DECK OR CABIN. WHEN THE RIGHT PACK WAS SELECTED ON & TO HIGHEST TEMP SETTING A FAINT MUSTY ODOR NOTED COMING FROM VENTS. DUPLICATED WITH ALL 3 BLEED SOURCES AT ANY POWER SETTING. REMOVED AND REPLACED RT PACK COALESCER BAG IAW AMM 21-51-13, AFTER REPLACEMENT OF BAG PERFORMED SAME OPS CHECK & UNABLE TO DUPLICATE ODOR.