Our detailed guide to the N57 engine in BMWs: Is it reliable and which versions to avoid?
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The BMW N57 engine , introduced in 2008, is a 6-cylinder in-line diesel engine widely adopted on several models of the brand, notably the BMW 3 Series (E90, F30), 5 Series (F10), 7 Series (F01) and various X models.
Known for its performance and driving pleasure, it nevertheless has some weaknesses that can compromise its long-term reliability . This article details the critical points of the N57 engine and solutions to preserve its durability.
1. Insufficient oil pressure at low engine speeds
One of the best-known weaknesses of the N57 engine concerns the oil pressure being too low at idle or low RPM.
Most often, no warning lights come on, making the problem difficult to detect before damage occurs.
Insufficient oil pressure can cause:
- accelerated wear of the connecting rod bearings,
- crankshaft fatigue ,
- or even complete engine failure in case of negligence.
Recommended solutions:
- Install a reinforced oil pump , which is more efficient at low engine speeds.
- Avoid prolonged engine idling .
- Turn off the engine if the stop exceeds one minute, especially in heavy urban traffic.
These simple actions help to preserve internal lubrication and considerably extend the engine's lifespan.
2. Fragile supply chain
Like many BMW engines of this generation, the N57 suffers from a timing chain prone to premature wear .
The guides and tensioners weaken over time, causing excessive play and a metallic rattling , particularly noticeable when cold.
Ignoring this noise can lead to timing misalignment , or even engine failure .
Recommended solutions:
- Perform oil changes every 10,000 to 15,000 km maximum , with a quality BMW LL-04 5W30 or 5W40 oil.
- Replace the timing chain at the first signs of abnormal noise.
- Avoid long journeys when the engine is cold and sudden accelerations when the engine is not warm.
Proper lubrication is essential, as dirty oil weakens the hydraulic tensioner , accelerating chain wear.
3. Fouling of the EGR system and intake manifold
The EGR cooler and exhaust gas recirculation valve are known to get clogged on the N57 engine.
Soot residue gradually accumulates, causing a loss of power , increased fuel consumption , and sometimes black smoke from the exhaust .
Fouling is particularly common on vehicles used mainly in cities or on short journeys .
Recommended solutions:
- Perform periodic cleaning of the EGR system and intake manifold (every 60,000 to 80,000 km).
- Run the engine at a sustained speed (after warming up) from time to time.
- Use a premium quality fuel (Excellium, Ultimate Diesel) to limit deposits.
In addition, an anti-fouling treatment can help keep the system clean between maintenance appointments.
4. Wear of connecting rod and crankshaft bearings
The N57 engine is powerful but its connecting rod bearings are a weak point .
Low oil pressure or infrequent oil changes lead to bearing wear, causing metallic noises when hot and, in extreme cases, engine bottom end failure .
Recommended solutions:
- Maintain frequent oil changes with approved BMW oil .
- Replace the connecting rod bearings preventively if the mileage exceeds 200,000 km.
- Listen carefully for any knocking noises in slow motion.
Rigorous maintenance is key to avoiding costly repairs often exceeding €5,000 .
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Overall reliability of the N57 engine: a good engine… provided it is maintained
The N57 remains an excellent diesel engine : torquey, quiet and pleasant to drive.
However, its maintenance must be followed meticulously :
- suitable oil, changed frequently
- regular monitoring of the distribution chain,
- monitoring of the EGR system and bearings.
A well-maintained example can easily exceed 300,000 km without major issues . Conversely, neglected maintenance can quickly lead to mechanical disaster.
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