What was found
(CAN) ON START UP THE CREW NOTICED SMOKE IN THE COCKPIT & CABIN. AFTER SOME TROUBLESHOOTING THE CREW SELECTED THE LT & RT ENVIRO SWITCHES TO THE OFF POSITION & THE SMOKE DISSIPATED. THE ACFT WAS INSPECTED & DISPATCHED UNDER THE COMPANY`S MEL PROTOCOL REQUIREMENTS. WHEN THE ACFT RETURNED FOR MAINTENANCE A POST INSPECTION WAS COMPLETED AND IT WAS DETERMINED THAT THE ACM WAS LEAKING OIL INTERNALLY. THE ACM WAS REPLACED WITH A SERVICEABLE UNIT. HIGH POWER RUNS WERE PERFORMED AND SYSTEM FUNCTIONAL CHECKS COMPLETED WITH NO FAULTS FOUND. THE ACFT WAS RETURNED TO SERVICE.