What was found
AIRCRAFT 5039, UPON SHUTDOWN OF BOTH ENGINES A BURNING OIL/DIRTY SOCK SMELL WAS OBVIOUS IN THE COCKPIT. APU BLEED WAS ON AND HAD BEEN ON. APU HAD 3 PLUS MINUTE WARM UP PRIOR TO APU BLEED. APU BLEED ON FOR 2 MINS. CORRECTIVE ACTION: STRONG WIND AND RAIN INTO TAILPIPE ON SHUTDOWN AT GATE. REMOVED NBR 2 INLET CONE AND FOUND OIL RESIDUE PRESENT. REPLACED #2 FAN SHAFT COVER "O" RING PER A321 AMM 72-15. PERFORMED DECONTAMINATION PROCEDURE A AND REPLACED RECIRCULATION FILTER CARTRIDGES. (LP 4868500)