Oil at turbine outlet
Problems with the oil drain system can cause leaks to appear in the turbo. When oil leaks appear at the turbine outlet, it usually indicates a problem in the oil drain system. Something has caused the oil to build up in the bearing housing to a height above the seals. Check the following items and correct them to eliminate the problem. Make certain that the turbo drain port is pointing down at not more than a 35 degree swing on either side of a vertical centerline. See that the oil drain line slopes downward its entire length, so that there is no place for the oil to collect in the line. New installations, especially, should be double checked and any "sink traps" eliminated. Aircraft with scavenger pumps do not need to eliminate sink traps, as the pump will provide positive suction.

Finally, check the drain lines. Those made from a rubber-lined, fabric covered hose may not cause any problems at all after running several years in one location. Even though the exterior of the hose looks fine, the rubber interior lining has become brittle. When replacing the turbocharger at the time of engine overhaul, it is very possible that such a drain line could be disturbed and bent, causing pieces of the brittle rubber to break off inside the drain line, partially obstructing the flow of oil. To prevent this from happening, always inspect the drain line when replacing a turbocharger.


i got the from http://www.approvedturbo.com/troubleshooting.htm

hope it helps.