BMW is a name synonymous with various traits in the automotive world, some of which have not been so favorable. Characteristics such as luxury, understated style, dynamic performance, and ever-increasing repair costs have made the brand both admired and critiqued. Historically, however, a common concern surrounding BMW ownership revolves around reliability, with many believing you must be prepared to invest heavily to maintain these vehicles.
There’s been a noteworthy shift in perception as reliability has reportedly improved; statistics from Consumer Reports indicate BMW currently ranks fifth in new car reliability and sixth for used cars. However, the brand still faces criticism regarding its maintenance costs, which sit at an unfortunate 25th place in affordability. That said, if you maintain your vehicle correctly, it may not be as significant of a problem.
Just like other car manufacturers, BMW isn’t without its faults, especially regarding its engines. Whether due to intricate designs, inherent flaws, recalls, or decision missteps, even a reputable name like BMW has its share of engineering excesses. Many engines are influenced by intricate electronic systems, precision components, and delicate systems that require diligent upkeep. Today, we’re shining a light on five such problematic powerplants that pose serious concerns for owners.
N47 I4 diesel: timing chain failures
Primarily available in European markets, the N47 diesel engine is a straightforward inline-four rig, either single or twin-turbocharged, with variations around 1.6L and 2.0L manufactured from the late 2000s to the early 2010s. Typically considered an average diesel engine, the N47 displayed commendable fuel efficiency in smaller models like the 1-series, and required minimal specialized maintenance—a rarity for a luxury German car. However, it earns a spot on this list due to one critical component: the timing chain.
The timing chain plays an essential role in keeping an interference engine like the N47 properly synchronized. If this timing mechanism fails or becomes misaligned, it can lead to catastrophic issues like piston and valve collisions. Timing chains are designed for durability, often lasting approximately 100,000 miles prior to replacement. Unfortunately, BMW designed this crucial component to be inaccessible without significant labor, positioning it at the rear of the engine. Rather than a recall, the company initiated a “technical campaign” to address the problem, leaving accessibility concerns for all models equipped with this engine.
N63 V8: Early variants were a hot mess
The N63 V8 engine, found in several models throughout the 2010s, is known for its unique handling of turbochargers. This twin-turbo setup features one charger for each cylinder bank, also termed a biturbo arrangement. Exhaust gases heat the turbochargers to high temperatures, a phenomenon worsened by the distance from the exhaust manifold which contributes to turbo lag.
Instead of positioning the turbos on the manifold, BMW chose to implement a “Hot-Vee” design, placing the turbos within the intake passage of the V8. Being the first biturbo and modern Hot-Vee engine from BMW, the N63 faced significant hurdles initially, particularly with heat management and oil consumption.
Early versions of the N63 were notorious for turbo malfunctions and overheating, paired with valvetrain failures leading to excessive oil use and pre-ignition issues. Fortunately, subsequent versions improved reliability, but buyers should remain cautious and ideally avoid pre-2012 N63 models; those who do consider them must keep a vigilant eye on engine temperatures and maintain regular oil checks.
S85 V10: Pay to play
There’s a certain thrill associated with a high-revving V10 that captivates enthusiasts. This is reflected in BMW’s S85 V10, which allows for breathtaking performance—provided you’re willing to bear its maintenance costs. While visually striking, the S85 V10 is often deemed less reliable than the underperforming group member in a collaborative project.
Issues primarily stem from the engine’s connecting rod bearings, which are essential for linking the piston head to the crankshaft. As these bearings wear more quickly than those in other engines, they raise the risk of bottom-end failure. Owners frequently share images of bearing failures online, evidencing the commonality of this issue. Coupled with high maintenance expenses, the S85 presents a double-edged sword: while it offers exhilarating driving, it comes with considerable financial demands related to upkeep, reflecting its motorsport lineage.
N54 straight six: rock-solid engine, terrible everything else
The N54 straight six, celebrated among tuning enthusiasts for its power potential and extensive aftermarket upgrades, might spark debate. One would expect such an engine to be overbuilt to handle its power output, leading to the question: what places it on the list of least reliable BMW engines?
Fundamentally, the engine itself is generally sound—factory models that receive proper maintenance remain reliable. However, the surrounding components can create a multitude of headaches. The high-pressure fuel pump is notorious for failing, leading to inadequate fuel delivery. Fuel injectors are often floored by leakages while the valvetrain faces its own issues with valve cover leaks. Additionally, the system is prone to turbo and boost leaks, alongside issues with parts like the water pump that require frequent replacements.
Though the N54 may hold legendary status among enthusiasts, it falls short in terms of reliability, primarily due to accessory problems. A broken component does not matter much when stranded by the side of the road due to engine complications.
N73 V12: German overengineering
BMW is renowned for its straight-six engines, yet to stand out, they took two of these engines and combined them into a common crankshaft to create the N73 V12. This engineering marvel, revered for its smoothness and power—ideal for luxury vehicles like the Rolls Royce Phantom—also carries with it a complex set of problems.
For owners, the steep costs associated with maintaining a V12 can be overwhelming, especially in flagship models like the BMW E65 7-series. Despite generally positive feedback regarding the engine’s performance, ensuring it runs optimally requires meticulous attention to detail, as well as noteworthy financial investment.
Our methodology
This analysis focuses on engines predominantly from the past 15 to 20 years, providing a robust selection to identify trends associated with reliability failures. Although modern engines may exhibit their own challenges, substantial time is typically required for issues to surface, while older engines can vary significantly in dependability based on care and usage.
We gathered insights from a variety of reputable sources, including well-regarded automotive publications, expert YouTube channels, forums, reports from long-term ownership experiences, and journalistic reviews. Our aim was to present diverse perspectives that inform owners of potential maintenance costs, issues, and the ease of accessing engine components.
The topics highlighted in our review specifically pertain to engine performance and functionality, including all essential accessories and components vital for the car’s operation. Other factors, such as transmission issues or running gear—which vary with model and year—are outside the scope of this investigation. Always ensure to check for active recalls and be aware that extreme mileage may intensify these known reliability problems.
