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BMW N55 Engine Problems: Causes, Solutions, Models Affected
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The N55 launched in 2009, incorporating the latest technology at BMW, considered "state of the art" at the time. One of the most significant innovations was the engine's turbocharging, which no longer used the two turbochargers (Bi-Turbo) of the N54 but rather a single Twin-Scroll charger. Furthermore, the third generation of the Valvetronic system made its debut in the N55, which has become more robust compared to previous generations.
BMW N55 Engine Problems
Despite many improvements, the N55 is far from flawless. In fact, the wide array of problems that plague this otherwise excellent engine can burn a significant hole in the owner's pocket. Below, we'll discuss the classic weaknesses that have caused much stir over the past ten years.
Defective Water Pump
In the N55, an electric water pump is used, known for its premature failures. It's not uncommon for a defect to be reported after roughly 93,205 miles, announcing itself with the warning "Engine temperature too high" on the instrument cluster and accompanied by an obligatory coolant loss.
Recommendation: A preventive replacement of the water pump along with the thermostat, which can also cause issues. It is advisable to use high-quality replacement parts to avoid the adage, "buy cheap, buy twice."
High Oil Loss / Oil Consumption
High oil loss or consumption is nothing unusual for the N55 and can amount to a quart every 600 miles. However, such consumption is not healthy for the engine itself or the catalytic converter. The reasons for oil loss or consumption can be traced back to several weaknesses:
Defective Valve Cover Gasket
The rubber-made valve cover gasket (VDD) hardens and becomes porous over time, allowing motor oil to make its way to the surface. Besides the resulting oil loss, oil can enter the spark plug wells, damaging the spark plugs.
A minor oil leak at the valve cover or gasket does not pose an immediate danger to the N55. However, the oil may drip on the catalytic converter, leading to smoke development and the smell of burnt oil in the cabin.
Defective Crankcase Ventilation
High oil loss or consumption may also result from a defect in the crankcase ventilation (KGE). As the KGE is integrated into the valve cover or the cylinder head cover, the latter must also be replaced.
Defective Oil Filter Housing
The oil filter housing is another weak point and can burst. The manufacturer is aware of the problem and has replaced the housing without question in the affected engines. For vehicles with many miles on the odometer, this issue may be absent.
If oil loss is detected in the area of the oil filter housing, it should not be postponed, as oil can drip on the serpentine belt. Over time, this leads to the belt's degradation and potential breakage.
VANOS Solenoid Valves
The VANOS solenoid valves are not made to last forever and will eventually fail. A defect is primarily noticeable in the lower RPM range through RPM fluctuations and a noticeable loss of power, occasionally accompanied by starting difficulties.
Carbon Formation in Intake Manifold and Valves
Due to direct gasoline injection, the N55 will struggle with coked injectors and carbon deposits in the intake tract. To delay the resulting problems (loss of power, higher consumption, etc.), it is advisable to use cleaning fuel additives regularly when refueling.
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BMW N55 Technical Information
| Model | Displacement | Power | Torque | Introduction |
|---|---|---|---|---|
| N55B30M0 | 182 cu in | 306 hp / 5,800 – 6,000 RPM | 295 lb-ft / 1,200 – 5,000 RPM | 2009 |
| N55B30M0 | 182 cu in | 306 hp / 5,800 – 6,400 RPM | 295 lb-ft / 1,200 – 5,000 RPM | 2013 |
| N55B30 | 182 cu in | 320 hp / 5,800 – 6,000 RPM | 332 lb-ft / 1,300 – 4,500 RPM | 2011 |
| N55B30O0 | 182 cu in | 326 hp / 5,800 – 6,000 RPM | 332 lb-ft / 1,300 – 4,500 RPM | 2011 |
| N55HP | 182 cu in | 340 hp / 5,800 – 6,000 RPM | 332 lb-ft / 1,300 – 4,500 RPM | 2013 |
| N55B30T0 | 182 cu in | 360 hp / 5,800 – 6,000 RPM | 343 lb-ft / 1,350 – 5,250 RPM | 2015 |
| N55B30T0 | 182 cu in | 370 hp / 6,500 RPM | 343 lb-ft / 1,400 – 5,560 RPM | 2015 |
Conclusion
Despite the numerous horror stories circulating online, the N55 is fairly reliable. As long as the mentioned weaknesses are monitored and financial reserves are kept for potential repairs, purchasing a BMW with this engine (e.g., in the 3 Series or X5) is generally unproblematic. However, the service history should be as complete as possible to avoid plunging headlong into a maintenance backlog.
Cars Equipped With BMW N55 Engine
| Series | Models |
|---|---|
| 1 Series | 135i, M135i, 1 Series M Coupe |
| 3 Series | 335i, 335xi, 335is |
| 4 Series | 435i, 435xi |
| 5 Series | 535i, 535xi, 535i Gran Turismo |
| 6 Series | 640i |
| 7 Series | 740i, 740Li |
| X Series | X3 xDrive35i, X4 xDrive35i, X5 xDrive35i, X6 xDrive35i |
| Other | M2, Z4 sDrive35i, Z4 sDrive35is |
Nick Marchenko, PhD
Industrial Engineer & Automotive Content Specialist
Nick writes in-depth guides on car clubs, engine specs, vehicle ownership, and modifications, combining engineering knowledge with automotive passion.
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