The N26 is the emission-friendlier alternative to the BMW N20 engine.
The BMW N26 engine, found only in North American versions of the previous-generation 2 Series, 3 Series, and 4 Series is reasonably reliable with proper maintenance. It isn't bulletproof, though, and Eric from the YouTube channel I Do Cars got his hands on a dead motor to see the damage that killed the engine.
For the uninitiated, the N26 is the greener version of the N20 inline-four, made in compliance with the SULEV legislation. The N20 was succeeded by the B48, a turbocharged four-pot mill fitted in smaller BMWs, Minis, and the Toyota GR Supra.
Eric always starts his teardown projects by turning the crank to see whether it is locked up. The N26 engine did turn, giving him a good start, but there were a few worrying signs of neglect. Some of the nuts were missing, and the valve cover was damaged, exposing the timing chain.
As the teardown progressed, it was found that the oil filter's condition was good, while the valve assembly wasn't necessarily faulty but somewhat dirty. What Eric noticed, though, was the different bolts used in the engine.
Upon dismantling the intake and exhaust manifolds, the ports looked fine. Removing the exhaust manifold also meant the turbocharger had to be pulled out. Eric inspected the turbo and saw the fins were bent.
Eric went on to remove the crank pulley and timing assembly to allow the cylinder head to be detached from the block. He did not disassemble the brand's Valvetronic system, however, not wanting to interfere with its resale value as an unopened unit.
With the cylinder head out of the way, Eric saw burn marks between the cylinder, indicating a damaged head gasket. Typically, head gaskets blow from an overheated engine, which seems likely since the heat tabs on the engine had melted.
Eric disassembled the oil pan and crankshaft assembly at the end of the teardown. The crankshaft, bearings, and pistons looked fine, but the top of the cylinder bores saw heat stains.
Engine reliability will always depend on how owners take care of their vehicles. Overheating would inevitably kill a power unit over time. Factors like a lousy cooling or oil system could cause temperatures to exceed the normal operating range, which could be prevented with proper maintenance.