My favorite BMW engine of this century isn’t any of the twin-turbocharged monsters in modern M cars, or even the absolutely brilliant B58 (that’s my second-favorite, though). Instead, my favorite BMW engine is the N52, the 3.0-liter naturally aspirated straight-six from cars like the E90 3 Series, F25 X3, and E60 5 Series. It’s a sensational engine, with unrivaled silky smoothness, a wonderful noise, and pretty surprising reliability. I’ve owned two N52-powered cars and both engines were bulletproof, even with high-mileage. However, things can always go wrong with even the most robust engines, especially when neglected. In M539 Restoration’s latest video, Sreten shows you what neglect can do to an N52 and how to fix it.
Not everyone who wrenches on their own cars is as handy as Sreten, has a garage full of lifts like he does, or the seemingly endless specialty tools that he has. So no one is expecting you to basically rebuild your engine like he does. However, there are a few interesting yet simple things in this video that almost anyone who’s a decent wrench can do to keep their N52 running properly for many, many more miles. For example, you probably aren’t going to order over $1,000 worth of specialty tools to take the cams out just to replace a seal that already looks OK. However, taking the valve cover off to check that seal isn’t a big deal, so it’s worth learning how to do to prevent a future problem without paying a shop to do it.
If you do have the money to spend on specialty tools, you likely can afford to have everything done by a reputable shop. But watching Sreten dig through the engine teaches you what goes wrong, what to look out for, and what these jobs actually entail. So if you do take your car to a shop, you’ll know if the mechanic knows their stuff.
What’s impressive about the N52 is that Sreten’s car has been, in his words, “tortured,” and yet still looks pretty good inside. While its roundabout 125,000 miles aren’t a lot for an N52 — one of mine had nearly 170,000 and ran like butter — Sreten’s had only a handful of oil changes in its long life and was seriously neglected. There’s quite a bit of gross oil gunk, in the valvetrain, but despite that there’s very little wear. So if a neglected and abused N52 looks surprisingly good, then a well-maintained one should last ages.
Sreten also starts to do the rod-bearings in this video, which is not a job for the average DIYer. The entire front subframe needs to come down, the engine needs to be supported, and the oil pan needs to be dropped so you can get to the bottom end. It’s useful to see, though, as even with such poor service history, the N52’s rod bearings, while worn, weren’t in terrible shape.
This video proves the durability of the N52, as even when neglected and abused, it can hold up surprisingly well. If well taken care of, it should last a lifetime. If you own one, this video is worth a watch, as it helps you understand your engine better, know where its common failure points are, and how to prevent wear and tear in the future.
