E46: how to avoid turbo failure

Written by william zane
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The E46 is the factory designation for the fourth generation of the popular 3 Series made by German manufacturer BMW. The E46 was powered by a variety of engines over its production run. There was also a high-performance variant called the M3 that was developed by BMW's Motorsport division. Unlike the E46's replacements, the E90 and E92, the E46 was never turbocharged as a way to get additional power from the engine. This has not stopped the aftermarket from developing turbo kits for the E46. Turbochargers can last a long time with the proper care, but if neglected can fail.

Skill level:
Moderately Challenging


  1. 1

    Let the turbo cool down for a few minutes after the BMW has been driven. If the engine is shut down suddenly when the turbo is hot, the supply of oil is suddenly cut off. This lack of lubrication on the turbo's bearings and internals can wreak havoc. Instead, let the engine idle for a minute or two. You can also install a turbo timer, which is a device that keeps the engine running for a predetermined period of time after the ignition key is turned off.

  2. 2

    Use synthetic oil. One of the most important aspects of maintaining an aftermarket turbo on an E46 is the use of proper oil. The company that made and installed your turbo conversion will have specifications for what type of oil to use. It is extremely important to use the synthetic oil, which resists thermal breakdown far better than conventional oil at the extremely high temperature that turbos produce.

  3. 3

    Oil the turbo after an engine oil change. When the oil is drained out of the engine, it is also drained out of the turbo. If the turbo does not have oil in it when it is started, it may overheat. Instead, remove the fuel pump relay and turn the engine over for a few seconds. The engine will not start without fuel and will deliver oil to the turbo.

  4. 4

    Change your oil frequently. Nearly all turbocharger units share the engine's oil supply, but as stated above, run far hotter than the engine itself. Because of this, it is paramount that you change the oil frequently in a turbocharged BMW. A good interval to change the oil is between 2,500 and 3,000 miles.

  5. 5

    Closely monitor the oil level in your engine. Again, due to the fact that the turbo shares the engine's oil supply for its lubrication, it is important that the oil level not drop to dangerous levels. Turbochargers can cause an engine to burn more oil than a normally aspirated engine, making this an important step in your maintenance routine. Check the oil once a week.

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