How to Diagnose Diesel Engine Turbo Chargers

Written by alexander eliot
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There are numerous problems that can develop with your diesel engine's turbo system. Small issues such as boost pressure leaks can lead to more complicated malfunctions if not diagnosed and repaired immediately. Luckily, modern turbo diesel engines feature an extensive airflow and emissions monitoring system. The engine control unit (ECU) constantly monitors engine parameters such as air intake, fuel delivery, and exhaust emissions. Any problem that arises throughout the turbo system generally will trigger an ECU error code, which will trigger the dashboard "Check Engine" light. Most other turbocharger issues can be diagnosed by ear under normal vehicle operation.

Skill level:

Things you need

  • ECU error code reader

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  1. 1

    Plug an ECU error code reader into your vehicle's ECU access port. Generally, this port is located in the interior driver's side footwell area. If you do not have an ECU code reader, many automotive parts and service retailers offer free error code reading services.

  2. 2

    Run the ECU error code reader program. This will give you a readout of any current error codes recorded by the ECU. Error codes also feature a brief description of the malfunction and/or affected engine parts, which makes for a quick and simple diagnosis.

  3. 3

    Drive your vehicle to a roadway on which you can safely and legally accelerate the engine to its rpm redline. Accelerate the engine under full throttle and listen closely to the turbocharger noise. Excessive turbo whining indicates worn turbocharger internals, such as the turbo shaft or ball bearings. In more extreme cases, a grinding noise may be present when the turbo spools. This is due to the turbo compressor wheel or other internals grinding against the turbo housing.

  4. 4

    Monitor the turbo boost pressure gauge during acceleration if your vehicle is equipped with one. A boost pressure gauge gives you a constant readout of the turbocharger's air output. If the boost value is inconsistent under acceleration, this indicates an air pressure leak somewhere in the turbo system. If the boost value spikes briefly upon acceleration, this indicates a worn or improperly set actuator, such as the actuator found on the turbo waste-gate or blow-off valve.

  5. 5

    Open the bonnet of your vehicle and visually inspect the various turbo system components. Most turbo systems feature various rubber vacuum lines. These lines are prone to work loose or crack over time, which allows for a boost pressure leak. Replace any damaged vacuum lines immediately. Also, check all of the various connections throughout the intercooler piping system, which connects the turbocharger to the engine throttle body. Intercooler piping systems feature various rubber adaptor connections. Ensure that all of these adaptors are tightly secured and free of damage.

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