Why the BMW N47 Engine is THE MOST Unreliable BMW Engine?

Introduction

The BMW N47 is a four-cylinder inline diesel engine, it’s the successor to the BMW M47 engine. It ranges from 1.6 to 2.0-liters in displacement and outputs 94 to 204hp as per the configuration. It, being a modern engine, complies with the stricter emission standards using EGR and DPF technology, which leads to some of the problems this engine faces. All the major and minor problems that you should expect when driving this engine are discussed below.

This engine has been fitted in the BMW 1 series, 5 series, and 3 series 4-cylinder diesel variants.

The Problems

Timing Chain Premature Failure

The timing chain inside the BMW N47 engine suffers from excessive wear and premature breakdowns. It can collapse while the engine is running, which causes serious damage to the engine. It mostly requires a complete engine replacement if the damage is severe or requires some major repairs. A failing timing chain can be diagnosed with a rattling noise from the rear side of the engine. The timing chain seats between the engine and the transmission at the rear end of the engine, thus requiring either the engine to be removed or the transmission to be detached to replace the timing chain.

EGR Sensor Malfunction

The EGR system was designed to help the car meet stricter emissions standards. It recirculates a part of the exhaust gases back into the intake to reduce the amount of nitrogen oxide. But this system starts malfunctioning when the sensor gets covered in soot. It then makes more and more exhaust air recirculate into the intake. The hot exhaust gases cause the plastic intake manifold to melt and leak out in some scenarios. This opened valve also results in a reduction in boost pressure.

A widely opened EGR valve can result in soot build up on the Fuel injectors, intake manifold and the glow plugs. It results in reduced airflow due to the restrictions and prevents the car from starting easily in winters.

PDF Not Working in Short Runs

DPF filters out soot or diesel particulate matter from the exhaust gases. It functionally operates under high temperatures. On frequent shorter journeys, this DPF does not get hot enough to remove the soot and exhaust gases manage to get out unfiltered. This results in soot build up on your turbo, DPF sensor, EGR sensor and even on your engines glow plugs.

Power Steering Pump Failure

The power steering pump is also not much reliable on these engines. A failing power steering pump can be identified from oil spillage around the cap of steering oil reservoir.

Crank Case Breather Hose Oil Leakage Under High Temperature

The rubber crank case breather hose leaks out typically under high temperature. This is indicated by oil leakage from the hose end. This problem was however resolved by BMW by replacing it with a stiffer plastic hose.

Conclusion

So, if you are among the owners of a car equipped with the BMW N47 engine, look out for the timing chain making any rattling noise, it is suitable to replace it around 60-100k miles. Do clean your car’s EGR sensor on timely oil changes to avoid unnecessary soot build in your intake and engine components. If you get a good deal on selling it, go for it as it is better to just avoid this engine, then to own and babysit it.