The BMW M division is known for making high-performance engines that perform brilliantly, but before the M240i coupe and X3 M40i crossover models along with other configurations of the B58 engine arrived below the bona fide M variants, BMW experimented with the idea by building some pretty cool cars that didn’t feature the most powerful letter in the world. Its first attempt at offering turbocharging for the masses was the twin-turbo N54, but although it is one of the best German straight-six engines reaching a new height of performance, this was plagued by issues. It was still popular in the USA, especially in the E82 135i and E92 335i coupe offerings. As a result, BMW later wanted to review the motor and created the new N55 with a single twin-scroll turbo. This motor was even used in the first M2. It’s not often that an M car shares an engine with what could be considered a base model. Nevertheless, even this engine is not completely care-free, so what should you look out for when dealing with a client wanting to buy this motor? Let’s take you through our top five preemptive maintenance aspects.
1 – Charge Pipe / Intercooler Boost Pipe
If you pop the hood on any modern engine, you’ll likely find a sea of plastics. The N55 is no different, but some of these plastic components can become a real problem. The charge pipe always becomes an issue. Sadly, this is not a matter of ‘if’ but rather ‘when’ it will become brittle, crack, and break. This causes a tremendous boost leak, resulting in the automatic triggering of ‘limp mode’ and the inability to safely drive the car. Although less common than the charge pipe, the boost pipe from the intercooler is also known to fail. Numerous aftermarket solutions are available and sourcing an aluminum charge pipe is easy. Even an increase from the standard 300 hp can’t kill the aluminum solution, which is the same size. For the cooler pipe, a simple silicone bend with some clamps will be a long-lasting solution.
2 – Oil Filter Housing Gasket
Despite this being a common issue on the N54 engine, the N55 also suffers from gasket failure near the oil cooler. When this gasket begins to warp, oil and water can mix and we don’t need to tell you how harmful that can be. Again, this will happen eventually and a new gasket will eventually fail too. Thus, we wouldn’t recommend replacing it before it goes. Rather, inspect the oil filter housing once or twice a week and sort it out when you notice some light sweating. It’s a quick fix that seats easily and doesn’t cost much either.
3 – VANOS Solenoid
The N55 features BMW’s version of V-TEC, known as VANOS. It’s a much more complex system but although it works very well and feels linear, it’s far from perfect. These solenoids are known to fail after mileage of 70,000 or so – sometimes sooner, sometimes later. Fortunately, you don’t necessarily have to replace these solenoids. Some brake cleaner applied onto a microfiber cloth can be used to lightly clean and polish these. If a test drive reveals that the clean didn’t work, then yes, you will need a replacement, but sometimes it’s just gunk and build-up that can be easily remedied.
4 – Valve Cover Gasket
Another gasket on this list that gives issues is the valve or tappet cover gasket. With heat and age, this gasket tends to warp over time too. Symptoms are minor, with a slight leak visible on the engine block and increased oil consumption. The leak is usually not major enough to be visible on your driveway, but there are cases where you may notice it tarnishing your paving. Fortunately, a replacement is cheap and it’s not a big job to do. Just remember to cross-tighten the valve cover bolts when you’re done and not to overdo it with the torque you apply to each bolt.
5 – Electric Water Pump
This is yet another issue inherited from the N54. Although cases of electric water pump motor failure are less prevalent than on the N54, they still occur with frequency. If this fails, the vehicle will go into limp mode to prevent any further damage. Unfortunately, this is not the easiest job to do and will require the removal of the front bumper to make it relatively comfortable to work on. However, it is worth noting that the E-Series N55 motors have this issue more often than F-Series vehicles. If you come across an electric water pump from an F-Series vehicle, the fabrication of a small bracket is all you will need to retrofit the newer pump. This will be the safest OEM-style way of sorting this out.
Another aspect of the N55 engine that you may wish to do some work on includes the PCV system. This valve is integrated into the valve cover itself and cannot be deleted. In comparison, Volkswagen’s 2.0-liter TFSI engine of the same era had the PCV system separated. When the diaphragm fails, a squeaky noise can be heard. If left unchecked, both your front and rear main seals can be affected, and these are not easily replaced. Sadly, this means you have to get a whole new valve cover just for the PCV valve. We’d also recommend getting your valves walnut blasted. A carbon clean is always an important part of keeping any direct-injection motor healthy and can actually improve your fuel economy, giving you better mpg.
We’d also keep our eye on the water system as a whole, as pipes and the end tanks on the radiator are made of plastic that becomes brittle and can form leaks or simply burst. Finally, we’d also recommend oil changes every 7,500 miles or so as BMW’s service intervals are a bit too far apart and various factors including heat and the way a car is driven can cause the oil to degrade earlier than expected. If you’re after more performance and intend to modify your vehicle, your limits will not only be determined by the cost of parts that provide more horsepower but also how much maintenance you’re willing to do. Other issues like the high-pressure fuel pump, crank hub, and turbo can start to cause issues with huge spikes in power and demands, but if you keep the engine relatively stock, these expensive parts won’t become an issue.