What was found
AIRCRAFT WAS GROUNDED: CREW REPORTED STRONG COCKPIT/CABIN ODOR/SMELL, FLIGHT AIR RETURNED PHL, EMERGENCY DECLARED. ACCOMPLISHED J/C 26L00021001, FOUND APU TO SOURCE OF CABIN ODOR. ACCOMPLISHED J/C 26L00021002, FOUND OIL ON LOAD COMPRESSOR, INLET, AND COMING FROM LOAD COMPRESSOR DRAIN LINE. REMOVED AND REPLACED APU OIL COOLER FAN IAW AMM 49-52-51 AND ACCOMPLISHED JOB CARD 26L00021004.