How to Diagnose Turbo Chargers

Written by alexander eliot
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Turbochargers increase the amount of airflow into an engine, which substantially raises the engine's horsepower potential. However, turbo systems are very complex, and therefore create the possibility for numerous malfunctions to occur. Modified engines are especially prone to turbo system issues, as increased boost pressure from the turbocharger creates additional stress on other engine components. Luckily, diagnosing most issues with the turbocharger system can be done by ear when you accelerate the engine.

Skill level:

Things you need

  • Screwdriver set
  • Socket wrench
  • Socket set

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  1. 1

    Drive your vehicle to a roadway on which you can safely and legally accelerate the engine to its rpm redline. Highway entrance ramps are often a good location for this. Accelerate the engine under full throttle, and allow the revs to climb to near the rpm redline.

  2. 2

    Listen closely to the noise of the turbocharger as you accelerate. Excessive turbocharger whine indicates failing turbo bearings or a worn turbo shaft. When these components wear out, the turbocharger shaft and compressor wheels develop play within the housing. This generates a loud whining noise, and will cause additional wear on the turbocharger. In extreme cases, worn turbo bearings will cause a loud grinding noise. If either of these noises are present, have your turbocharger rebuilt or replaced as soon as possible.

  3. 3

    Monitor the turbo boost pressure gauge as you accelerate. If the boost pressure spikes briefly under heavy acceleration, this generally indicates a boost leak in the system. Common places for boost leaks to develop include the turbo wastegate, blow-off valve, and various vacuum lining. Boost leaks will also cause an inconsistent boost value after the boost spike occurs. If your vehicle lacks a boost gauge, pay special attention to the engine response under acceleration. A boost spike will cause the engine to surge suddenly as you are already accelerating. Inconsistent boost pressure will cause the engine to feel hesitant when revving.

  4. 4

    Inspect the turbo compressor shaft visually if you are still unsure whether or not your turbo is malfunctioning. Allow plenty of time for the engine to cool off, then open the bonnet to access the engine compartment. Remove any components that restrict access to the turbocharger inlet. Generally, this includes the engine cover components and exhaust manifold heat shield. Detach the air intake hose from the turbocharger inlet by loosening the intake hose ring. You do not need to remove the intake entirely, as long as you can fit your fingers into the turbocharger inlet.

  5. 5

    Reach into the turbocharger inlet and grip the end of the compressor shaft. This is the shaft connected into the middle of each turbo compressor wheel. Firmly push the compressor shaft up and down. Any play in the compressor shaft indicates worn turbocharger bearings. With very minor play, most turbochargers will still function normally. However, excessive shaft play indicates a failing turbocharger. After you have checked the compressor shaft, replace the air intake and any other engine components that you removed. If you discovered there to be shaft play, have your turbocharger rebuilt or replaced as soon as possible.

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