BMW N55 engine can be said to be BMW’s ace engine, in all model series have applications, so many owners have similar problems. This engine has a rattling fault incidence that is relatively high, the specific failure phenomenon is as follows.
There are several possibilities for BMW N55 rattles.
- The car can be heard in the engine compartment out of the noise, most of the shrill screeching, whistling, of course, may also be squeaking, etc.
- The general engine idling will appear when the noise and the feeling of rattling are more obvious, the engine speed reaches 1500r/min when the noise is gradually reduced to 2000r/min, and the noise basically completely disappears.
- Open the oil filler port, and the noise disappears, close the oil filler port, and the noise reappears.
If the fault phenomenon of your car matches the above description, then 90% is caused by the crankshaft oil seal aging/damage, you can listen carefully to the source of the sound, if it is the rear of the engine, then it is the crankshaft after the oil seal, if the noise is coming from the front of the engine, then the problem is in the crankshaft before the oil seal. Replacing the appropriate oil seal will solve the problem.
The reason for the noise is: Due to the crankshaft oil seal aging/damage/insufficient rigidity, it can’t ensure the vacuum sealing of the crankcase. When the engine is in the self-absorption mode, that is, idling, a certain amount of negative pressure will be generated inside the crankshaft, and the sealing lip of the oil seal will lift to generate the noise under the action of the negative pressure.
If, in addition to the above malfunction phenomenon, you experience a similar noise while driving, there is a high probability that the crankcase pressure regulator is damaged, because this regulator is diaphragm-type. If the regulator is damaged, for example, there exists a small gap, the whistling sound is easily produced under the action of the pressure, like the sound of a brisk wind blowing through a small hole. In this case, since the regulator is integrated into the valve cover, you usually have to replace the entire valve cover.
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