What was found
DIRTY SOCK SMELL ON DESC ENT CREW STATES SMELL WAS COMING FROM FWD CABIN/FLIGHT DECK...PACK 1 DID INSPECTION OF APU PER AMM TASK 49-00-00-200-812-A NO OIL, FUEL OR HYDRAULIC LEAKS FOUND ON GROUND WITH APU BLEED ON AND BOTH PACKS ON, NOTED AN OIL SMELL IN COCKPIT AND FWD GALLEY AREA. PERFORMED IDLE ENG RUN OF ENGS 1 AND 2 TO ISOLATE WHERE ODOR WAS COMING FROM. WITH ENG 1 BLEED AND LH PACK ONLY, NO SMELL. WITH ENG 2 BLEED AND RH PACK ONLY, NO SMELL. UPON ENG SHUTDOWN WITH APU BLEED ON, STRONG OIL SMELL AND BURNING RUBBER WAS NOTED IMMEDIATELY IN COCKPIT. FURTHER T/S REQUIRED. REF AMM 71-00-00 AND TSM 05-50-00-810-831-A "TYPE 1" STEP RECOMMENDED NEXT TO FIND THE CAUSE REMOVED AND REPLACE BOTH RECIRC FILTER CARTRIDGE PER TOMC REQUEST REF AMM 21-21-41 AFTER RECIRC FILTERS WERE CHANGED RAN PACKS WITH APU BLEED FOR OVER 20MINS. COULD NOT DUPLICATE SMELL. REF AMM 21-00-00-615-802-A PARTS USED: 31-2121-3-0008,QTY :1