What was found
ON CLIMBOUT THE PILOT REPORTED THAT VISIBLE SMOKE AND A SLIGHT OIL SMELL WAS PRESENT WHEN HE TURNED THE BLEED AIR ENVIRONMENTAL SYSTEM ON. THE PILOT SHUT OFF THE ENVIRONMENTAL BLEED AIR SYSTEM AND RETURNED TO KPHX AND LANDED WITHOUT INCIDENT. MAINTENANCE PERFORMED A GROUND RUN AND COULD NOT DUPLICATE THE SMOKE OR OIL SMELL. FURTHER INVESTIGATION REVEALED THAT ENGINE OIL WAS PRESENT ON THE INLET SCREEN OF THE LEFT ENGINE. REMOVED THE LEFT ENGINE OIL FILTER HOUSING ASSEMBLY AND REPLACED THE HOUSING O-RING AND BACK UP RING. GROUND RUN LEFT ENGINE NO OIL WAS PRESENT AT THE ENGINE INLET SCREEN AREA. NO SMOKE OR OIL SMELL REPORTED ON SUBSEQUENT FLIGHTS.