Bmw N52 Engine Problems. The VANOS check valves on the side of the engine silt up with age one of mine was filthy. Usually the solenoid valve fails or the servo drive runs out.
If youre scouting out a BMW with an N52 engine make sure it has the updated cylinder head introduced in the 2009 models. It is a shame though that the N52s merits have been largely forgotten in the turbocharged wake of the N54. This is due to thin oil rings which are carbonized rather fast.
The N53 uses the same HPFP as the BMW N54 and these issues are well documented.
The N52 is known for its reliability for fun share the highest mileage youve seen on a surviving N52 engine. Needless to say this caused an oil leak. My car has 92k miles I think its just about broken in. High Pressure fuel pumps were such an issue when the engine first came out that BMW issued a recall on the engine.