Look at your logbooks. Was the wastegate or controller recently changed and how much time is on your turbocharger. The wastegate butterfly could be sticking due to carbon buildup or TIS (time in service) Check the lines to both the controller and wastegate for leaks. If your controller was recently changed out, the settings might need to be adjusted. Lots of times they are overly field adjusted. Mark where you start and move in small increments.

No repairs allowed. Must be replaced with balanced wheel(s) and checked for internal damage. Even the smallest nicks can set the wheel(s) off balance causing vibration which can cause major internal damage and turbocharger failure. The earlier caught, the better.

Your bearing housing is deteriorating, causing exhaust leaks.

On Garrett systems that have a gravity drain you should idle at least 4-5 minutes. Systems that are scavenged require 2-3 minutes and Rajay systems don’t require any at all.

The wastegate butterfly valve is sticking. Try some mouse milk on the bushings.

The absolute controller is adjusted too far in. The wastegate is closing too early making the PRV relieve the extra upper deck pressure.

The compressor and turbine housings need to be rotated per the installation instructions.

Some controller types can be field adjusted to help with manifold boost. Two such are the Variable Absolute Pressure Controller and the Density Controller. Examples following:

• To increase manifold pressure turn adjusting screw counterclockwise.
• One full turn should give you one inch.
• Recommend turning counterclockwise 2 full turns, if too much back up slightly.

To adjust density:

• On square adjusting bolt, turn clockwise to increase manifold pressure.
• Approx. 1/4″ turn should suffice.

The latest revision of Lycoming Service Instruction No. 1187 sets forth procedures and required equipment for adjusting density controllers in the field.

The outlet check valve is bad, allowing oil to fill the bearing housing past the point of the seal ring.