How to fix BMW Engine howling noise

BMW engine appear howling noise, check following to see how our mechanic fix it.

Vehicle information

Model: BMW 740Li

Year: 2009

Engine: N54


Fault symptom

During the driving of the car, howling noise appear suddenly, and it will be heard after stepping on the accelerator or just starting.


Fix process

1. Fault code “Boost pressure is too low” read by diagnose scanner.

2. Possible causes:

A. Air intake pipe is leaking.

B. Turbocharging is not working or damaged.

C. The boost pressure reducing valve is faulty.

3.Test driving several times and heard the sound coming from the turbocharger. It could be a leak or damage at the turbine. Check the two turbine impellers with an endoscope, as shown below:


Two impellers look a little different. Put the car on top and listen to the sound coming from one impeller, remove intake pipe and found that the impeller were damaged.

4. What damaged the impeller? Check that the pipe seal behind the air filter is missing and find that a lot of rubber debris is in the pressurized intake duct, indicating that this entry into the turbine caused damage to the impeller.


5. Disassemble turbocharge, found that the impeller were severely damaged, and the axial direction was also shaken.

6. The solution is to replace a new impeller. After replacement, the engine works normally without noise.


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