BMW N55 Engine Warning: How a Simple Belt Failure Can Destroy Your Engine The BMW N55 engine, found in numerous models such as the 335i, 435i, and various X and M-performance series vehicles, is renowned for its performance and smooth turbocharged power delivery. However, it harbors a critical design flaw that can lead to catastrophic engine failure At the heart of this issue lies the serpentine drive belt system. This belt runs multiple accessories such as the alternator, power steering pump, and air conditioning compressor. In the N55, the drive belt rides on a crankshaft pulley (also called the harmonic balancer) at the front of the engine. Under normal conditions, this setup works reliably. But when oil contaminates the belt, a dangerous cascade of events can unfold. The Root Cause: Leaky Oil Filter Housing Gasket The most common culprit for belt contamination is a leaking oil filter housing gasket (OFHG). Positioned directly above ... read more