What was found
FLIGHT 2135 EN-ROUTE, DIRTY SOCK SMELL ON TAKEOFF. ONLY COULD BE SMELLED IN FLIGHT DECK. FLIGHT ATTENDANT DID NOT SMELL ANYTHING ON MAIN CABIN. PACKS 1 & 2 ON, ENG BLEED ON, APU WAS OFF. AT REDUCTION OF POWER 1000 FEET SMELL WENT AWAY. THE FLIGHT RETURNED TO FIELD & LANDED WITHOUT FURTHER INCIDENT. FOUND ENG NR 1 WETTED WITH OIL. SEE LP 1285192 FOR ENG CHANGE INFORMATION. AFTER ENG CHANGE COMPLIED WITH JC 43L00072001, 43L00021001, 43L00072001, 43L00021001, 43L00036002 & 43T40072004. ALSO REPLACED RECIRCULATION FILTERS IAW AMM 21-24-02 & CABIN SUPPLY DUCT ITEM 30 ON IPC 21-24-03 FIG 01.