The turbocharger cannot be repaired. The entire unit must be replaced if there is a major mechanical defect. However, you can determine whether or not the seals or bearing are defective, meaning that the unit must be replaced.
Inspect the turbocharger exhaust outlet for excessive deposits of hard carbon. These deposits, not to be confused with light layer of normal exhaust soot, indicate oil is leaking past the bearing seal on the exhaust side and forming the carbon due to exhaust heat. Replace the unit.
Inspect the intake of the turbocharger for heavy accumulations of fresh oil. There will normally be some oil here because of the PCV system. If you suspect a leak, check axial (in and out) or radial (side-to-side) play in the turbocharger bearing. Use a dial indicator. The limit for axial play is 0.0035 in. (0.88mm) while the limit for radial play is 0.0067 in. (0.170mm)
If the engine exhibits severe detonation, the waste gate may be inoperative. Disconnect the waste gate control hose at the waste gate and seal it. Then apply 7–9 psi (48–62 kPa). This must be precisely controlled or the waste gate diaphragm may be damaged. Watch the waste gate to see if it operates. If the waste gate does not move, replace the diaphragm. If this does not cure the malfunction, replace the unit.
If the pressure hose to the waste gate is cracked, replace it.