What was found
ON CLIMB OUT, THE PILOT REPORTED THAT AFTER THE CABIN BLEED HEAT WAS TURNED ON, THE COCKPIT RAPIDLY FILLED WITH SMOKE. THE PILOT TURNED THE BLEED HEAT OFF & COMPLETED THE SMOKE IN COCKPIT CHECKLIST, THE SMOKE DISSIPATED. THE PILOT NOTIFIED ATC OF THE ISSUE, RETURNED & LANDED WITHOUT INCIDENT. MX FOUND AN OIL LEAK PRESENT ON THE LT ENG. INSPECTED THE LT ENG & FOUND THE FLEXIBLE OIL LINE TO THE LT AUTO FEATHER MANIFOLD LEAKING OIL FROM BEHIND THE B NUT FITTING. THIS OIL LEAK CAUSED OIL TO DRAIN INTO THE ENG INLET AREA CAUSING THE SMOKE IN THE COCKPIT WHEN THE BLEED HEAT WAS TURNED ON. R & R THE FLEXIBLE OIL LINE PN 330995F4-0314 WITH A SERVICEABLE LINE. LT ENG GND RUNS COMPLETED, OIL LINE LEAK CHECK WAS SATISFACTORY. TIME IN SERVICE OF THE REMOVED OIL LINE IS UNKNOWN. THIS LINE IS ON CONDITION PART.