A turbocharger system increases engine horse power by means of an exhaust gas-driven turbine that turns an impeller, or compressor, which in turn pressurizes the air entering the intake manifold. The turbocharger assembly is composed of two separate castings, the housing for the turbine is cast iron and the housing for the compressor is aluminum. The waste gate valve is designed to restrict the maximum boost level by allowing some of the exhaust gases to bypass the turbine when boost pressure gets too high. The wastegate controller solenoid valve keeps the wastegate controller closed to optimize the pressure on the outlet side of the compressor. The air bypass valve reduces the braking effect on the turbocharger by routing the excess air back to the turbocharger inlet duct. The turbocharger is lubricated by engine oil pumped through the turbocharger housing by the engine oil pump. You can inspect some things yourself such as a cracked turbo mounting flange, a blocked or restricted oil supply line, a worn out or overheated turbine/compressor shaft bearing or a defective waste gate actuator.