GM/Detroit 6.5L TURBOCHARGER – INSPECTION

Turbochargers are extremely reliable units. The majority of inoperative turbochargers are caused by dirt in the oil, oil lag (lack of oil flow), foreign objects or debris entering the turbocharger, and plugged or restricted air cleaner systems.

Lack of power, black smoke, blue smoke (excess oil consumption), or other engine performance problems are frequently blamed on the turbocharger when the actual cause is really another engine component. This is why a complete inspection of the turbocharger and all other engine components that may cause similar condi­tions must be examined before replacing the turbo­ charger. Refer to SECTION 6A for diagnosing engine problems other than those caused by the turbocharger.
The following steps and the preceding diagnostic chart will aid in diagnosing problems caused by the turbo­ charger. If it is determined that the turbocharger is the cause of the problem it must be replaced. Service of the turbocharger is not recommended.

Inspect

• A high pitched whine may indicate an exhaust leak or a leak in the air induction system.
• A cycling up and down in pitch often indicates a blockage in the air inlet duct, a restricted air clean­er, or a build up of dirt on the compressor wheel of the turbocharger (oil film is normal).
• A sharp, high pitched scream may indicate that the bearings have deteriorated and one (or both) of the wheels is rubbing on its housing (this results in blue exhaust smoke).
•  At the compressor wheel blades (figures 4 through
7). There should not be any bent, broken, eroded, or cracked wheel blades.
• At the housing for signs of rubbing.
• At the compressor wheel for a build-up of dirt.

important
• With this engine application, the inside of the air intake duct (rubber inlet elbow), turbocharger compressor wheel and housing can be quite oily, due to the venting of the crankcase vapors
into the air intake system. This is considered
normal.
• The CDR valve does not prevent oil vapors from getting into the turbocharger compressor inlet system.

CAUTION; Do not feel any components of the turbocharger while the engine is running. Make sure that the turbocharger has stopped rotating and the turbocharger and engine have cooled down before handling. Rotating parts and extreme heat may cause serious personal injury if handled.

• Carefully grasp the compressor wheel nut with fin­gers and rotate the wheel in a clockwise direction. It should turn freely with no signs of binding or scraping (housing contact).

• How the turbocharger rotates while pushing in and
pulling out on the compressor wheel; it should
rotate freely with no contact with the housing.

• Carefully grasp the compressor wheel nut with fin­gers and while rotating move the wheel up and down (radially). There should be no compressor wheel to housing contact. Note: axial and radial play is normal even on a new turbocharger. If compressor wheel to housing contact exists, it will be very evident when rotating the wheel. The wheel will drag or scrape on the housing surface and visual damage will be evident on the wheel blades and housing surface.

Important
If the turbocharger does not pass any one of the above inspections that indicate damage to the turbo­charger, with the exception of the waste-gate actuator, then the turbocharger must be replaced. See “Inspec­tion of the Waste-Gate Actuator.”

 

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