What was found
FLT 761, LGA-PBI. DURING IDLE DESCENT AT 5000 FT ENTERING CLOUDS HAD DIRTY SOCK SMELL IN COCKPIT; PERFORMED T/S STEPS PER INFO NOTICE 2017-T015F ALSO RECEIVED VERBAL DEBRIEF FROM CREW ABOUT ODOR PRESENT ON GROUND IN LGA. DURING APU INSPECTION WITH BLACKLIGHT, NOTED SIGNIFICANT SIGNS OF OIL IN APU PLENUM, COMPRESSOR CAGE, AND SATURATED TURBINE SHAFT AND BLADE SECTION. ALSO NOTED APU OIL LEVEL EXCESSIVELY LOW. ACCOMPLISHED LEVEL A ECS DECON W/ ENG BLEED PER AMM 21-00-00-615-802-A. NO SMOKE OR ODOR NOTED AFTER 20 MINUTES. REF LP DEFECT 3153706 ITEM 2 FOR APU DEFERRAL. A/C OK FOR CONT SVC AT THIS TIME. AFTER PERFORMING APU WASH. FOUND OIL EVIDENCE AT TOP CEILING OF APU COMPARTMENT TRACED IT BACK TO APU COOLING FAN. OIL PUDDLE NOTICED INSIDE OF COOLING FAN. R & R COOLING FAN IAW AMM 49-52-51. OPS CK LEAK GOOD THIS CLEARS MDDR 438355 MX-4 UPDATED PLACARD REMOVED MCC NOTIFED