What was found
AFTER STARTING APU AND TURN-ON BLEED AIR CABIN BEGAN TO FILL WITH AN OILY ODOR. SHUTDOWN APU AND STARTED BOTH ENGINES AND SMOKE DISSIPATED AND DID NOT RETURN. RE-ENABLED APU. VISUALLY INSPECTED APU EXAUST AND EXTERNAL COMPONENTS. NO LEAK OR DEFECTS NOTED. CHECKED OIL LEVEL FOUND TO BE OVERSERVICED TO TOP OF FILLER NECK. CLEANED AND INSPECTED COALESCER IAW CE680 MM 12-11-03 AND HONEYWELL RE100 (CS) MM 49-20-00. RAN FOR 30 MIN. NO DEFECTS OR ODOR NOTED.