BMW's turbocharged four-cylinder engines from the mid-2010s have garnered a reputation for being unreliable. This negative perception stems from several issues, with the most significant being the brittle plastic timing chain guides, which led to a failure in this specific engine. The I Do Cars YouTube channel recently acquired a failed N26 four-cylinder engine for its latest teardown video, providing an in-depth look at the reasons behind the frequent failures of these engines.
One prevailing theory is BMW's recommendation of a 15,000-mile oil change interval, which allows varnish and sludge to accumulate inside the engine, damaging the plastics and rubber components. This engine appears to corroborate this theory, as evidenced by the dark brown-stained metal in the head. As Eric, the video's host, delves deeper, he discovers chunks of the original plastic timing chain guides. His findings culminate at the oil pickup tube, which is completely blocked by pieces of the timing chain guide.
The abundance of these chunks obstructed the oil's path to the pump, depriving the engine of essential oil and causing extensive wear and damage. Interestingly, many of the engine's internals were salvageable, offering a silver lining. Nowadays, BMW advises changing the oil every 10,000 miles—a significant reduction from before, but still not as frequent as the 5,000 to 7,000-mile interval that might be advisable. If this teardown is any indication, prioritizing oil changes is crucial. Neglecting them could result in costly repairs down the line.
