What was found
THE PILOT REPORTED AN UNUSUAL AMOUNT OF OIL WAS BEING CONSUMED, AND ON HIS INBD FLIGHT THE OIL PRESSURE GAUGE WAS FLUCTUATING. THERE WERE NO VISIBLE SIGNS OF AN EXTERNAL OIL LEAK. ON THE GROUND RUN MX ALSO NOTED THE TORQUE WAS FLUCTUATING. WHEN BLEED AIR WAS TURNED ON A FINE MIST OF OIL WAS EMITTED FROM THE HEATER VENTS. TROUBLESHOOTING FOUND THE ENGINE VENT LINE HAD COLLAPSED INTERNALLY PRESSURIZING THE CASE AND CAUSED THE OIL TO LEAK INTERNALLY INTO THE COMPRESSOR.