What was found
DIRTY SOCK ODOR AFTER ENGINE SHUTDOWN, STRONG IN ALL AREAS, ALSO LESS ODOR WHILE DESCENDING THROUGH A CLOUD LAYER. PERFORMED TSM TASK 21-00-00-810-801-A. PERFORMED A NR 1 AND 2 ENGINES RUNS. ISOLATED ODOR, ORIGINATING FROM APU BLEED. REPLACED APU IAW TASK CARD 4901-9401, OPS & LEAK TESTED OK. NO OIL ODOR WITH APU BLEED AND PACKS 1 & 2 ON. OK FOR SERVICE.