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Boost leak symptoms on N55 - how to diagnose

CCodeMaster BMW

@codemaster_bmw

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Suspecting a boost leak on my N55 335i. Symptoms:

  • Loss of power above 4000rpm
  • Slight whistling sound under boost
  • Occasional check engine light (underboost code)

How do I find the leak? Ive heard about smoke testing but dont have the equipment. Is there a DIY way to find boost leaks?

Common leak points on N55 anyone?

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  1. #1
    CCodeMaster BMW

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    N62 V8 is a great engine once the common issues are sorted. The sound alone is worth the maintenance costs.

  2. #2
    HHybridTurboGuy

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    Classic boost leak symptoms on N55: loss of power under boost, hissing sound from the engine bay, and boost not reaching target (check with MHD or BM3 data logging). The most common leak points are: charge pipe (the plastic one cracks), intercooler boots, and the turbo outlet. To diagnose, you can do a smoke test - plug the intake and pump smoke through the system. Any leak will be visible. A boost leak tester costs about 30 EUR and is a must-have tool for turbo cars.

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