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A turbocharger is an integral component of a diesel engine’s powertrain, providing additional power and torque to the engine. But a turbo failure can cause many problems affecting a vehicle’s performance.

This blog will explore what happens when a turbo goes out on a diesel and how to diagnose and repair the issue.

Signs Of A Bad Turbo On A Diesel Car

Decreased Performance

If the turbocharger is not pushing enough air into the engine, it will not be able to generate the same power output as when it was working correctly. This can be especially noticeable when accelerating, as the engine will take longer to reach higher RPMs.

Excessive Smoke

The smoke can be either white, blue, or black, depending on the specific issue with the turbocharger. If the turbocharger leaks oil, the smoke will be blue. If the turbocharger begins to break down, the smoke will be white or black.

Strange Noises

When the turbocharger fails, it can produce a variety of strange noises. Most commonly, this includes a whining, hissing, or whistling sound. This noise is caused by the turbocharger not spinning correctly and its delicate parts failing.

Check Engine Light

Sometimes, the check engine light will illuminate. The computer detected a problem with the engine, and the cause may be related to the turbocharger. There isn’t a Turbo fault warning light on the dashboard. A check of the code for a bad turbo usually produces a P0299 code.

High Oil Consumption

A failing turbocharger can cause the engine to consume more oil than normal. This is because the turbocharger cannot generate the same amount of pressure, which can cause the engine to suck in more oil than it needs. If the oil level drops quickly, it may indicate that the turbocharger is beginning to fail. 

Engine Overheating

Finally, if the turbocharger is not working properly, it can cause the engine to overheat. This is because the turbocharger cannot generate enough air pressure to cool the engine, which can cause the engine to run hotter than normal. 

What Causes A Diesel Cars Turbo To Fail?

Poor Maintenance

Diesel cars require regular maintenance to ensure that the turbocharger is kept in good condition. . Regular oil and filter changes are necessary to extend the turbocharger’s life.


This occurs when the turbocharger is exposed to extreme heat, such as extended periods of driving at high speeds or in hot and humid climates. 

The high temperatures can cause the turbocharger to expand, leading to cracks and other damage. To prevent overheating, it’s important to ensure that the vehicle is well-ventilated and that the cooling system is in good condition.

Excessive Boost Pressure

The turbocharger relies on boost pressure to produce the additional horsepower and torque needed for the engine to perform at its best. However, when the boost pressure is too high, it can cause the turbocharger to fail. This is usually the result of a faulty boost pressure regulator setting.

This can be checked and altered by using a boost gauge or a boost pressure test. A boost gauge is used to measure the amount of pressure being produced by the turbocharger or supercharger. If the pressure in the gauge doesn’t increase as the engine speeds up, the turbocharger is most likely not functioning properly.

The first step in a boost pressure test is ensuring your vehicle’s engine is properly warmed up. This will ensure that the engine operates at its optimal temperature, which is important for accurate readings.

Oil Contamination

Oil contamination is another common cause of failure. The oil inside the turbocharger is responsible for lubrication and preventing premature wear. If contaminated, it can cause the turbocharger to fail. Contamination can be caused by poor maintenance or metal shavings from a failing engine.

Excessive Exhaust Backpressure

The turbocharger relies on exhaust gases to drive the turbine, which in turn drives the compressor. If the exhaust backpressure is too high, the turbo can be damaged. Excessive backpressure can cause the turbo to spin faster, increase the temperature and overheat, damaging the bearings, blades, and seals. 

This usually results from a faulty exhaust system or a clogged catalytic converter.

Age and Wear

Turbochargers can fail due to age and wear. They can last up to 150,000 miles if regular oil changes have been done.

What Parts of The Turbo Go Bad?


The wastegate is a valve responsible for regulating the exhaust gas that enters the turbocharger. It does this by opening and closing a port, allowing more or less exhaust gas to pass. If the wastegate fails, it can cause the turbocharger to spin too fast, resulting in engine damage.


The bearings support the turbine shaft and compressor wheel, allowing them to spin at speeds of up to 150,000 rotations per minute.

The most common cause of turbo-bearing failure is insufficient or bad oil.

If the bearing is not receiving enough oil, the components may become excessively hot, resulting in premature wear and eventual failure. 

Other causes of turbo bearing failure include poor quality or contaminated oil, incorrect bearing preload, and excessive bearing clearances.

Signs of turbo bearing failure may include increased vibration, grinding or rattling noises coming from the turbocharger, a decrease in turbo performance, and visible oil leakage.

Turbo Compressor Wheel

The job of a turbo wheel is to help create exhaust pressure in the engine. This is done by spinning a turbine wheel at high speeds, creating a vacuum that pulls air from the exhaust manifold into the engine.

A turbo wheel can fail due to problems with the bearings, shaft, or seals. Additionally, some turbo wheels can fail due to an imbalance in the wheel itself, which can occur if the wheel is damaged or worn down over time as it impacts the turbo housing.

Oil Seals

Turbo oil seals ensure that oil pressure is maintained in the turbocharger. 

They do this by sealing the turbine shaft, preventing oil from leaking out of the turbo. Various issues, including high operating temperatures and failing bearings, can cause them to fail. 

Typical signs of failure include oil leaks, decreased oil pressure, and a decrease in turbo performance.

In Conclusion

Many issues with a turbocharger, including excessive smoke, whistling noises, a check engine light, high oil consumption, and overheating, can cause decreased performance.

Drivers need to keep an eye on their turbocharger to ensure it is running correctly, as it can significantly affect the engine’s performance but, more importantly, result in a very expensive repair or replacement being required. 

Recognizing a bad turbo early can result in saving thousands of dollars.

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