The Ultimate BMW N55 Engine Guide: Tech, Performance, and Problems

When the horsepower wars of the late 2000s simmered down, BMW turned its focus to a more nuanced powertrain philosophy: efficiency. In this new era of reduced fuel consumption and tighter emission standards, the wizards of Bavaria set forth to create an engine that could satisfy the ever-growing thirst for performance while maintaining a green conscience.

Enter the BMW N55 engine, a masterclass in the art of balancing power with responsibility, and a testament to the brand’s relentless pursuit of innovation. Ladies and gentlemen, allow me to introduce you to the star of this month’s “The Power Plant” feature: the mechanical marvel that is the BMW N55.

N55 Specifications

SpecificationN55 Engine Data
Engine TypeInline-6
Displacement3.0 L (2,979 cc)
Bore x Stroke84.0 mm x 89.6 mm
Compression Ratio10.2:1
Horsepower300 hp
Torque300 lb-ft
TurbochargingSingle Twin-scroll
Fuel InjectionDirect Injection
ValvetrainDOHC, 4 valves/cylinder
Cooling SystemWater-cooled
Exhaust SystemIntegrated into the cylinder head
Engine ManagementBosch MEVD17.2.6
Emission Control3-way catalytic converter, EU6 emission standard
Redline RPM7,000 rpm
Fuel RequirementPremium Unleaded (91 RON or higher)
Oil Capacity6.5 liters (6.9 quarts)
Engine WeightApprox. 195 kg (430 lbs)
ApplicationsBMW 1, 3, 4, 5 Series, X3, X4, X5, X6, and others
Please note that these specifications represent general information for the N55 engine and may vary depending on the specific model year or application. The performance figures are based on the standard engine configuration, and special editions or performance variants may exhibit different characteristics.

The Birth of the N55 Engine

Born from the ashes of its award-winning predecessor, the N54, the N55 engine stepped onto the scene in 2009 with a symphony of technological advancements. Boasting a twin-scroll turbocharger in place of the N54’s twin-turbo setup, this straight-six genius demonstrated how the careful orchestration of engineering and design can lead to a harmonious blend of performance and efficiency.

And it didn’t take long for the N55 to become a household name, as its widespread adoption across the BMW lineup turned it into a beloved member of the family.

Throughout this article, we’ll delve into the heart of the N55 engine, dissecting its innovations in design, improved fuel efficiency, and emissions. We’ll also explore its omnipresence across various BMW models and touch upon common problems that have surfaced over the years.

So buckle up, BIMMERIST enthusiasts, as we embark on a thrilling journey into the world of the BMW N55 engine, where efficiency and performance intertwine in perfect harmony.

Technological Advancements

Single Twin-Scroll Turbocharger Instead of Twin-Turbo Setup

The N55’s pièce de résistance is its twin-scroll turbocharger, which replaced the N54’s twin-turbo configuration. This ingenious move allowed BMW to simplify the design, reduce weight, and cut costs, all while delivering a more linear power delivery.

Twin-scroll technology separates exhaust gases into two separate channels, allowing the turbocharger to spool up faster and maintain boost pressure more efficiently. The result is an engine that offers an impressive torque curve, even at low RPMs.

N55 Twin-Scroll Turbocharger. BMW Group

Improved throttle response and reduced turbo lag

The twin-scroll turbocharger is not just an exercise in efficiency; it also plays a critical role in enhancing the N55’s driving experience.

N55 Twin-Scroll Turbocharger Closeup. BMW Group

By reducing turbo lag and improving throttle response, this technology ensures that the engine delivers power in a more predictable manner. Drivers can now enjoy a seamless surge of acceleration, providing a thrilling driving experience that is unmistakably BMW.

Valvetronic Variable Valve Lift System

Another innovative aspect of the N55 engine is its Valvetronic variable valve lift system. This technology allows the engine to continuously adjust valve lift and duration, leading to optimized fuel consumption and emissions. By precisely controlling the amount of air that enters the combustion chamber, Valvetronic enables the engine to achieve greater efficiency without compromising performance.

Valvetronic doesn’t stop at fuel efficiency; it also contributes to the N55’s overall responsiveness. By controlling valve operation, the system allows for more direct and immediate throttle response. This gives the driver a heightened sense of connection to the engine and a more engaging driving experience – a hallmark of BMW’s engineering prowess.

Direct Fuel Injection

The N55 also features direct fuel injection, which delivers fuel directly into the combustion chamber with unparalleled precision. This technology ensures a more complete combustion process, resulting in increased power output and reduced emissions.

Direct fuel injection plays a crucial role in minimizing emissions by ensuring that the air-fuel mixture is perfectly balanced. This not only contributes to the N55’s compliance with stringent emission standards but also reinforces BMW’s commitment to producing cleaner, more sustainable vehicles.

Fuel Efficiency and Emissions

When it comes to fuel efficiency and emissions, the N55 engine represents a significant leap forward compared to its N54 predecessor. Thanks to the combination of its twin-scroll turbocharger, Valvetronic variable valve lift system, and direct fuel injection, the N55 delivers a more efficient powertrain without sacrificing the performance that BMW enthusiasts crave.

As emissions standards grew increasingly stringent in the late 2000s and early 2010s, automakers were tasked with finding innovative ways to reduce their vehicles’ environmental impact. The N55 engine was BMW’s answer to this challenge, achieving compliance with regulations such as Euro 5 and later Euro 6 standards, as well as the U.S. EPA Tier 2 Bin 5 standards. This impressive feat showcased BMW’s ability to adapt and excel in a rapidly changing landscape.

Real-world Fuel Economy Improvements

BMW’s focus on efficiency with the N55 engine is not just about meeting regulatory requirements; it also translates to tangible benefits for drivers. Real-world fuel economy improvements can be observed across the range of vehicles equipped with the N55, providing savings at the pump and a reduced carbon footprint. The N55’s marriage of performance and efficiency proves that responsible driving doesn’t have to come at the expense of driving pleasure.

Contribution to BMW’s sustainability efforts

The N55 engine is a prime example of BMW’s commitment to sustainability and reducing its vehicles’ impact on the environment. By combining innovative technologies and engineering solutions, BMW has demonstrated that it is possible to create a high-performance engine that respects the planet. As a result, the N55 serves as a benchmark for future engine development and an important milestone in BMW’s ongoing journey toward more sustainable mobility.

Widespread Adoption Across the BMW Lineup

The N55 engine made its debut in the 2010 BMW 535i, instantly earning acclaim for its performance and efficiency. This marked the beginning of a new era for BMW powertrains, as the company showcased its ability to blend high-performance engineering with environmentally conscious design.

As the N55 continued to prove its worth, BMW expanded its presence across the brand’s lineup. This versatile engine found its way into numerous models, demonstrating its adaptability and suitability for a wide range of driving experiences.

  1. 1 Series
  2. 3 Series
  3. 4 Series
  4. 5 Series
  5. 6 Series
  6. 7 Series
  7. X3, X4, X5, and X6

From compact sports sedans to luxury grand tourers, the N55 engine’s seamless integration into various models solidified its status as a cornerstone of BMW’s powertrain offerings.

Performance and competition-oriented models (M135i, M235i, and 335i)

Beyond its widespread adoption in the standard BMW lineup, the N55 engine also found its way into performance and competition-oriented models. Vehicles such as the M135i, M235i, and 335i benefitted from the N55’s marriage of power and efficiency, resulting in exhilarating driving experiences that pushed the limits of what was possible from an inline-six engine. These performance models served as a testament to the N55’s versatility and prowess, further cementing its place in BMW’s history.

The BMW N55 engine has found its way into some of the most iconic and popular models in BMW’s lineup, providing a remarkable balance of power, efficiency, and responsiveness. In this section, we will explore how the N55 engine drives and performs in various BMW models, showcasing its versatility and dynamic character.

BMW 3 Series (F30 335i)

As the heart of the F30 335i, the N55 engine delivers an engaging driving experience, with smooth power delivery and exceptional responsiveness. The N55’s torquey nature makes the 335i feel agile and quick, allowing it to sprint from 0 to 60 mph in just over 5 seconds.

BMW F30 335i. BMW Group

The engine’s strong mid-range power ensures rapid acceleration for highway overtaking maneuvers, while its linear power curve allows for easy, predictable control.

MORE: Buyer’s Guide to the BMW F30: Performance, Technology, and Common Issues

BMW 4 Series (F32, F33, F36 435i)

In the F32 435i, the N55 engine brings sporty performance to BMW’s 4 Series coupe. With a wider, more aggressive stance and a lower center of gravity compared to the 3 Series, the 435i exhibits impressive handling characteristics that complement the N55’s robust power output.

BMW F32 435i. BMW Group

The combination of the N55 engine and the 4 Series chassis results in a thrilling and engaging driving experience, making it an excellent choice for enthusiasts who value both performance and style.

BMW 5 Series (F10 535i)

The N55 engine powers the F10 535i with a level of performance that is both refined and exhilarating. Although the 5 Series is a larger, more luxurious sedan, the N55 engine propels it with surprising vigor, achieving 0 to 60 mph in around 5.5 seconds.

BMW F10 535i. BMW Group

The engine’s smooth power delivery and seamless torque ensure a comfortable and responsive ride, perfectly complementing the 5 Series’ composed and sophisticated character.

MORE: BMW F10 535i: The Ultimate Buyer’s Guide for the Ultimate Driving Machine

BMW X3 (F25 xDrive35i) and X4 (F26 xDrive35i)

In BMW’s X3 and X4 crossovers, the N55 engine proves its adaptability by delivering spirited performance in a more versatile package. With BMW’s xDrive all-wheel-drive system, the N55-powered X3 and X4 models offer impressive acceleration, reaching 0 to 60 mph in the low 5-second range.

BMW F26 X4 xDrive35i. BMW Group

The engine’s torque-rich character and responsiveness make these crossovers feel nimble and eager, despite their higher ride height and increased weight compared to their sedan counterparts.

The N55 engine’s widespread use across BMW’s lineup speaks volumes about its well-rounded capabilities and dynamic character. Whether powering a sporty coupe or a luxury crossover, the N55 engine consistently delivers engaging performance and driving enjoyment. Its combination of efficiency, power, and smooth operation makes it a fitting powerplant for some of BMW’s most popular models, providing drivers with an unforgettable driving experience.

Here’s a performance table showcasing the key performance figures for the BMW models powered by the N55 engine:

Model0-60 mph (seconds)Top Speed (mph)HorsepowerTorque (lb-ft)
F30 335i (3 Series)5.1155*300300
F32 435i (4 Series)5.1155*300300
F10 535i (5 Series)5.5155*300300
F25 xDrive35i (X3)5.3150300300
F26 xDrive35i (X4)5.2150300300
*Top speed is electronically limited.

Please note that these figures may vary slightly depending on the specific model year, transmission, and optional equipment. The performance figures are based on the standard N55 engine configuration, and special editions or performance variants may exhibit different performance characteristics.

Common Problems and Solutions

High-pressure Fuel Pump Issues

The high-pressure fuel pump (HPFP) is a critical component in the N55 engine’s direct fuel injection system. It ensures that fuel is delivered to the combustion chamber at the precise pressure required for optimal performance and efficiency.

However, some N55 engines have experienced HPFP failures, a problem that also plagued its predecessor, the N54. Symptoms of HPFP failure can include rough idle, reduced power, hesitation under acceleration, and, in severe cases, engine stalling. Drivers may also notice the check engine light illuminating, indicating a potential issue with the fuel system.

Causes of failure

The exact cause of HPFP failure can vary, but common reasons include manufacturing defects, internal wear, or contamination in the fuel system. In some cases, the HPFP can degrade over time due to normal wear and tear, while in other instances, it may fail prematurely.

BMW’s response and extended warranty

Acknowledging the issue, BMW has taken proactive measures to address HPFP failures in both the N54 and N55 engines. The company has provided extended warranties on the HPFP, covering the cost of repairs or replacement in the event of a failure. This warranty extension demonstrates BMW’s commitment to supporting its customers and ensuring the reliability of its vehicles.

Preventative measures and maintenance

Although HPFP failure is a known issue, it is essential to note that many N55 engines have not experienced this problem. Regular maintenance, such as fuel system cleanings and using high-quality fuel, can help prevent HPFP failure.

Additionally, owners should pay close attention to any symptoms that may indicate an issue with the HPFP and seek professional assistance if they suspect a problem.

By staying vigilant and addressing issues as they arise, drivers can minimize the risk of HPFP failure and continue to enjoy the performance and efficiency that the N55 engine offers.

Water Pump and Thermostat Failures

The N55 engine uses an electric water pump, a component that offers several benefits over traditional mechanical water pumps. Since an electric water pump is not driven by the engine’s serpentine belt, it operates independently of engine speed.

This independence allows for more precise control of the cooling system, ensuring optimal engine temperature regardless of engine load or RPM. Moreover, an electric water pump can improve overall engine efficiency, as it only draws power when needed, reducing parasitic losses associated with mechanical water pumps.

The cooling system in the N55 engine plays a crucial role in maintaining optimal engine temperature and ensuring reliable performance. Two critical components of this system are the electric water pump and thermostat. The water pump circulates coolant throughout the engine, while the thermostat regulates the flow of coolant based on the engine’s temperature. Both components work together to prevent overheating and maintain the engine’s efficiency and longevity.

Symptoms of electric water pump failure

Electric water pump failure can manifest in several ways. Symptoms may include engine overheating, coolant leaks, reduced cabin heating, or a check engine light with cooling system-related fault codes. In some instances, the water pump may fail to activate, leading to a lack of coolant circulation and subsequent engine overheating. In other cases, the pump may run continuously, causing excessive cooling and potentially affecting engine performance.

Causes of electric water pump failure

There are several potential causes of electric water pump failure in the N55 engine. One common issue is the failure of internal components within the pump, such as the electric motor or impeller. Over time, these components can wear out or become damaged, leading to pump failure. Another possible cause is electrical issues, such as wiring problems, damaged connectors, or faults in the control module that governs the water pump’s operation.

How Long Do Electric Water Pumps Last in the N55 Engine?

When comparing the N54 and N55 engines’ electric water pumps in terms of reliability, both engines have had their share of water pump failures. However, over the years, BMW has made improvements in the design and quality of the electric water pumps used in these engines, which has contributed to increased reliability.

The N54 engine, being an earlier design, experienced more frequent water pump failures, with some pumps failing as early as 40,000 miles (64,000 kilometers). These failures were often attributed to manufacturing defects, normal wear, and tear, or electrical issues.

With the introduction of the N55 engine, BMW made efforts to address some of the issues observed in the N54’s cooling system, including improvements to the electric water pump. While the N55’s electric water pump is not immune to failures, as mentioned earlier, it is generally considered to be more reliable than the N54’s water pump. The average lifespan of the N55’s electric water pump is between 60,000 and 100,000 miles (97,000 to 160,000 kilometers), although individual experiences may vary.

Oil Leaks

Oil leaks are not uncommon in the N55 engine, with the oil filter housing gasket and valve cover gasket being the most likely culprits. Regular maintenance and inspection can help identify these issues early, allowing for timely repairs and preventing more severe problems down the road.

Oil leaks in the N55 engine can occur from various sources, with the most common culprits being the oil filter housing gasket and the valve cover gasket. Over time, these gaskets can degrade or become damaged, resulting in oil seepage and potential leaks:

Oil filter housing gasket

The oil filter housing gasket is responsible for sealing the interface between the oil filter housing and the engine block. As the gasket ages, it may become brittle and lose its sealing ability, causing oil to leak from the oil filter housing area.

Valve cover gasket

The valve cover gasket is located between the valve cover and the engine’s cylinder head. It seals the gap between these components, preventing oil from leaking out of the engine. Over time, the valve cover gasket can also become brittle, crack, or degrade, resulting in oil leaks.

Repair costs

Repair costs for oil leaks in the N55 engine can vary depending on the specific issue and the labor rates in your area. Here are some approximate repair costs for the most common oil leak sources:

Oil filter housing gasket replacement

The cost to replace the oil filter housing gasket can range from $300 to $600, depending on the labor rates in your area and whether any additional components need to be replaced during the repair, such as the oil cooler gasket.

Valve cover gasket replacement

Replacing the valve cover gasket can be more labor-intensive and, therefore, more expensive. The repair cost for this issue can range from $600 to $1,200, depending on labor rates and whether other components, such as the valve cover itself or ignition coils, need to be replaced during the repair.

Preventative measures and maintenance

Regular maintenance and inspection can help identify potential oil leaks early, allowing for timely repairs and preventing more severe problems down the road. Routinely checking the engine for signs of oil leaks, such as visible oil stains or a burning oil smell, can help you catch issues before they worsen. Regular oil changes with high-quality oil and genuine BMW oil filters can also contribute to the overall health of your N55 engine and help minimize the risk of oil leaks.

Timing chain and VANOS issues

While less common than the previously mentioned issues, some N55 engines have experienced timing chain and VANOS (Variable Nockenwellen Steuerung) system failures. These issues can lead to severe engine damage if not addressed promptly. Regular maintenance and inspection of the timing chain and VANOS system are critical in preventing costly repairs.

Solutions and preventative measures

Despite these known issues, the N55 engine remains a reliable and robust power plant for many BMW models. Regular maintenance, including oil changes, coolant flushes, and inspections, can go a long way in preventing problems and ensuring the longevity of the engine. By addressing any issues as they arise and taking proactive steps to maintain the engine, owners can continue to enjoy the thrilling performance and efficiency that the N55 engine delivers.

Timing chain and its role in the engine

The timing chain in the N55 engine is responsible for synchronizing the rotation of the crankshaft and camshaft, ensuring proper valve timing during the engine’s operation. The timing chain is designed to last the lifetime of the engine; however, in some cases, it may experience premature wear or failure, which can lead to severe engine damage if not addressed promptly.

VANOS system and its function

VANOS (Variable Nockenwellen Steuerung) is BMW’s variable valve timing system, which adjusts the camshaft timing based on engine load and RPM. This system helps optimize engine performance, fuel efficiency, and emissions by ensuring that the valves open and close at the ideal times during the combustion cycle. In some cases, the VANOS system in the N55 engine may experience issues, such as solenoid failures, causing suboptimal valve timing and reduced engine performance.

Symptoms of Timing Chain and VANOS Issues

Symptoms of timing chain issues may include a rattling noise from the engine, especially during startup, poor engine performance, or misfires. In severe cases, a broken timing chain can lead to catastrophic engine failure.

VANOS-related issues may manifest as rough idle, loss of power, reduced fuel efficiency, or a check engine light with fault codes related to the VANOS system. In some cases, VANOS issues may be intermittent, making them more challenging to diagnose.

Causes of Timing Chain and VANOS Issues

Timing chain issues in the N55 engine can be caused by manufacturing defects, inadequate lubrication, or the use of low-quality materials. Additionally, extended oil change intervals or the use of poor-quality oil can contribute to premature timing chain wear.

VANOS issues can be caused by several factors, such as solenoid failures, worn or damaged camshaft gears, or issues with the VANOS control module. In some cases, oil sludge or debris in the engine oil may also affect the proper functioning of the VANOS system.

Preventative measures and maintenance

Regular maintenance and inspection of the timing chain and VANOS system are critical in preventing costly repairs and ensuring the longevity of the N55 engine. Adhering to proper oil change intervals, using high-quality oil, and regularly inspecting the timing chain for signs of wear can help minimize the risk of timing chain issues.

For the VANOS system, regular oil changes and using the correct oil type can help prevent oil sludge and debris buildup, which can affect the system’s performance. Additionally, keeping an eye out for any symptoms related to VANOS issues and addressing them promptly can help maintain the engine’s performance and efficiency.

Turbocharger issues

The N55 engine features a single twin-scroll turbocharger, which enhances engine performance by increasing power and torque while minimizing turbo lag. However, some N55 engines have experienced issues with the turbocharger, such as wastegate rattle or failure of the turbocharger itself. Symptoms of turbocharger issues may include loss of power, poor engine performance, excessive exhaust smoke, or whining noise from the turbocharger area.

Causes of failure

Turbocharger issues can arise from various factors, including manufacturing defects, wear and tear, or oil supply issues. Wastegate rattle can result from wear in the wastegate mechanism, causing the wastegate flap to vibrate and produce a rattling noise. Turbocharger failure can be due to worn or damaged internal components, such as the turbine or compressor wheel, or issues with the turbocharger’s bearings.

Solutions and maintenance

Addressing turbocharger issues often involves repairing or replacing the affected components. In some cases, a wastegate rattle may be resolved by adjusting or replacing the wastegate mechanism. For more severe turbocharger failures, replacing the entire turbocharger may be necessary.

To prevent turbocharger issues, it is essential to follow proper maintenance procedures, such as regular oil changes with high-quality oil, and ensuring that the turbocharger receives an adequate oil supply. Regularly inspecting the turbocharger for signs of wear or damage, and addressing any symptoms of turbocharger issues promptly, can help maintain the N55 engine’s performance and reliability.

Carbon build-up

Direct injection engines, such as the N55, are prone to carbon build-up on the intake valves, which can negatively impact engine performance and efficiency. Symptoms of carbon build-up may include rough idle, reduced power, poor fuel efficiency, and hesitation under acceleration.

Carbon build-up in the N55 engine is primarily caused by the engine’s direct injection design. Since fuel is injected directly into the combustion chamber, it bypasses the intake valves, which would typically be cleaned by fuel vapors in a port injection engine. As a result, oil and fuel residues can accumulate on the intake valves over time, leading to carbon build-up.

To address carbon build-up, thorough cleaning of the intake valves is necessary. This process may involve walnut shell blasting, chemical cleaning, or manual scraping to remove the carbon deposits. Regular maintenance, such as oil changes with high-quality oil, can help reduce the rate of carbon build-up.

Using a catch can system to separate oil vapors from the PCV system can also help minimize carbon build-up on the intake valves. Additionally, periodically performing an Italian tune-up (driving the vehicle at high RPMs under load) can help burn off some of the carbon deposits.

Rod Bearings Wear

Rod bearings play a crucial role in the N55 engine by providing a smooth surface for the connecting rods to ride on the crankshaft. Over time, these bearings can wear or become damaged, leading to potential engine issues. Symptoms of rod bearing issues may include knocking noises from the engine, reduced oil pressure, or, in severe cases, engine failure.

Rod bearing failure in the N55 engine can be attributed to manufacturing defects, inadequate lubrication, or the use of low-quality materials. Additionally, aggressive driving or extended oil change intervals can contribute to premature rod bearing wear.

Addressing rod bearing issues may involve replacing worn or damaged bearings. In some cases, more extensive engine work may be required, such as machining the crankshaft or replacing it entirely.

To prevent rod bearing issues, it is essential to follow proper maintenance procedures, such as regular oil changes with high-quality oil, and using the correct viscosity and oil type recommended by BMW. Keeping an eye on oil pressure and listening for any unusual engine noises can also help detect potential rod-bearing issues early.

Ignition Coils

Ignition coils are responsible for transforming the battery’s low voltage into the high voltage required to ignite the fuel-air mixture in the combustion chamber. Over time, ignition coils in the N55 engine can fail, leading to misfires and reduced engine performance. Symptoms of ignition coil issues may include rough idle, loss of power, check engine light with misfire-related fault codes, or poor fuel economy.

Ignition coil failure can be caused by manufacturing defects, heat-related damage, or electrical issues such as voltage spikes. Additionally, extended service intervals or the use of low-quality replacement coils can contribute to premature ignition coil failure.

Replacing the faulty ignition coils is the primary solution for addressing ignition coil issues. It is recommended to use genuine BMW or high-quality aftermarket ignition coils to ensure optimal performance and longevity.

Fuel Injectors

Fuel injectors in the N55 engine are responsible for delivering precise amounts of fuel into the combustion chamber. Over time, these injectors can become clogged or wear out, leading to issues with fuel delivery and engine performance. Symptoms of fuel injector issues may include rough idle, poor acceleration, reduced fuel efficiency, or a check engine light with fuel-related fault codes.

Fuel injector issues can arise from various factors, such as manufacturing defects, the use of low-quality fuel, or contaminants in the fuel system. Additionally, extended service intervals can contribute to fuel injector wear or clogging.

Addressing fuel injector issues often involves cleaning or replacing the affected injectors. In some cases, using a fuel system cleaner can help remove deposits and restore injector performance. For more severe issues, it may be necessary to replace the faulty injectors with new, genuine BMW or high-quality aftermarket injectors.

Regular maintenance of the fuel system, such as changing the fuel filter and using high-quality fuel, can help prevent

Issues covered by BMW Service Bulletins and SIBs (Service Information Bulletins)

BMW Service Information Bulletins (SIBs) are issued to provide technical information and solutions to BMW technicians to address specific issues that have been identified in certain models, including the N55 engine. These bulletins cover a range of issues, from minor fixes to more serious concerns, and help ensure that BMW owners receive consistent and accurate solutions to known problems.

Examples of N55 issues covered by SIBs

Engine coolant temperature sensor replacement

BMW issued a SIB addressing the inaccurate reading of the engine coolant temperature sensor in some N55 engines. This issue could result in the engine operating at higher temperatures than indicated, potentially leading to overheating. The SIB recommends replacing the coolant temperature sensor with an updated version to resolve the issue.

Engine Oil Cooler Thermostat

Some N55 engines have experienced issues with the engine oil cooler thermostat, which may not open at the correct temperature. This issue can cause the engine oil to overheat and potentially damage internal engine components. BMW issued a SIB to replace the faulty thermostat with an updated design.

High-Pressure Fuel Pumpe (HPFP) Software Update

To address the high-pressure fuel pump issues mentioned earlier, BMW issued a SIB recommending a software update for the engine control module (ECM). This update improves the operation of the high-pressure fuel pump, helping to prevent potential failures and improve engine performance.

Turbocharger Wastegate Rattle

As discussed earlier, some N55 engines have experienced wastegate rattle issues with the turbocharger. BMW issued a SIB outlining the proper repair procedures, including the replacement of the wastegate actuator and adjustment of the wastegate mechanism to eliminate the rattle.

By addressing the issues covered in BMW SIBs and following the recommended maintenance procedures, N55 owners can help prevent common problems, maintain their engine performance, and enjoy a more satisfying ownership experience.

N55 BMW Service Bulletins


SIB120516/ N55 – Engine Malfunction Warning Due to Vapor Forming in the Fuel System

SIB123814/ N20, N26, and N55 Engines with Injector Electrical Faults

SIB120915/ N55: Slight Surging at Constant Speeds when Accelerating Very Lightly


SIB121611/ N55 Engine Failsafe – FC 120308 Boost Pressure Control, Plausibility: Pressure Too Low Stored in DME Fault Memory


SIB121514/ N55 with Double-Clutch Transmission: Idle Fluctuates when Stopped

SIB120912/ N55: Intermittent Loss of Power

SIB121313/ N55 Engine Does Not Start on First Attempt when Cold

SIB123914/ N55: Engine Briefly Shudders or Runs Erratically After Cold Start

SIB121713/ N55: Engine Difficult to Start at Cold Ambient Temperatures

SIB122012/ N55 Engine: DME FC 160502 Crankcase Ventilation Heater Activation

SIB124014/ N55 and NPOW: DME Fault 102001, Air Mass Too High, Sets in ECO PRO Mode

SIB110814 Att/ Recall Campaign 14V- 176: N55 Engine – Replace VANOS Gear Bolts

SIB123314/ Fault Code 1D2008 Stored in DME


SIB120113/ Transmission Intermittently Goes into “P” or “N” after MSA Engine Start

SIB120415/ DME Internal and Valvetronic Faults Set at Cold Ambient Temperatures

SIB010515/ In-Tank Fuel Delivery Module (Pump): Limited Warranty Extension to 10 Years Without Mileage


In conclusion, the BMW N55 engine has earned its place as a remarkable powerplant in the annals of automotive engineering. By integrating innovations in design, such as the single twin-scroll turbocharger and improved fuel efficiency and emissions, BMW has created an engine that seamlessly balances performance, efficiency, and driving enjoyment. Its widespread adoption across the BMW lineup speaks to its versatility and well-rounded capabilities.

While the N55 engine does have some common issues, such as high-pressure fuel pump concerns, water pump and thermostat failures, and timing chain and VANOS problems, staying informed about these issues and adhering to proper maintenance practices can help prevent problems and ensure the longevity of the engine. As with any performance-oriented engine, regular inspection and timely attention to potential issues are critical to maintaining optimal performance and reliability.

The N55 engine’s performance in popular BMW models like the 3 Series, 4 Series, 5 Series, and X3/X4 crossovers demonstrates the dynamic character and engaging driving experience it offers. Through continuous refinement and a commitment to engineering excellence, BMW has created an engine that provides drivers with an unforgettable experience, leaving an indelible mark on the world of automotive engineering.

MORE: BMW F10 535i: The Ultimate Buyer’s Guide for the Ultimate Driving Machine

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Georg Meier

BMW technician since 1996. I began my automotive journey in 1993 as an apprentice mechanic at Automag, the world's oldest BMW dealership in Munich. With years of experience and dedication, I garnered a wealth of knowledge about the intricacies of BMW and MINI vehicles. The love/hate relationship with the brand led me to found BIMMERIST where I share expertise and insights with fellow enthusiasts.

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