How to Fix BMW N55 Engine Noise
BMW N55 Engine Noise Overview
The BMW N55 engine is a popular choice among BMW models and is known for its performance. However, it is also prone to developing a rattling noise. This article will discuss the possible causes of this noise and how to fix it.
Symptoms of BMW N55 Engine Noise
- Engine noise can be heard from the engine compartment, usually a shrill screeching or whistling sound. It could also be a squeaking sound.
- The noise is more noticeable when the engine is idling. As the engine speed reaches 1500r/min, the noise gradually decreases. At 2000r/min, the noise almost disappears.
- Opening the oil filler port makes the noise disappear. Closing it causes the noise to reappear.
Causes and Solutions
Cause 1: Crankshaft Oil Seal Aging/Damage
- If the fault phenomenon matches the above description, there is a 90% chance that the crankshaft oil seal is aging, damaged, or lacks rigidity. This can lead to a lack of vacuum sealing in the crankcase.
- When the engine is in self-absorption mode (idling), a certain amount of negative pressure is generated inside the crankshaft. Under the action of this negative pressure, the sealing lip of the oil seal lifts and creates noise.
- Solution: Listen carefully to the source of the sound. If it is from the rear of the engine, it is the crankshaft rear oil seal problem. If the noise comes from the front of the engine, it is the crankshaft front oil seal issue. Replacing the appropriate oil seal will solve this problem.
Cause 2: Crankcase Pressure Regulator Damage
- If there is a similar noise during driving in addition to the above symptoms, there is a high probability that the crankcase pressure regulator is damaged.
- The regulator is diaphragm-type. If it is damaged, for example, there is a small gap, a whistling sound can be produced under pressure, similar to the sound of a strong wind blowing through a small hole.
- Solution: Since the regulator is integrated into the valve cover, usually the entire valve cover needs to be replaced.
