BMW Engines to avoid + why BMWs are unreliable

Every year on the most luxurious and reliable vehicle list features one of the most iconic vehicle brands – BMW. At the same time, for some strange reasons, BMW still features in the unreliable car list. That may sound confusing but read on because this article will help you understand and identify BMW engines to avoid.

The BMW driving experience is exciting, memorable, and unmatched by most brands. The excitement stops with the motors because the worst BMW engines are pain and pure agony to own.

5 BMW Engines to avoid

The engines we are about to discuss have various challenges from bearable failures to outright engine write off. The first most unreliable BMW engine is…

BMW Engines to avoid - S85B50 V10 ENGINE

This 5.0L engine powers the M5 – E60 / E61 and M6 – E63 / E64 made between 2005 to 2010. It is a powerful rig and packs a whooping 500hp in raw power. Unfortunately, the problems with this engine are endless… one of the most unreliable BMW engine.

BMW S85 engine problems

The M series has some of the least reliable BMW models. It is important to understand the problems expected by owning a vehicle in this category. The BMW S85 engine problems includes:-

Constant wear on Rod bearings – This engine has at least 20-rod bearings which means you could be looking at a very expensive fix in parts and labor when they wear. Figuratively you could pay $3,000+ to replace those bearings. To detect the failure in the early stages look out for ticking sounds at idle and low RPMs. You can also pick the problem in the early stages by checking for metal shavings in engine oil at service.

Throttle actuators failure – Located between the air filter and the engine, this component is responsible for air control in the engine for combustion. The more air it lets into the chambers the better the combustion and engine performance. The reverse applies. That means when the throttle actuator fails, the engine gets air chock and the most common symptom is the car going into limp mode. A replacement is necessary to fix the issue.

S85B50 V10 ENGINE IN THE E60 M5

Idle actuators failure – You are likely to get a DSC failure message on the center console and also a start assist failure notice when the idle actuator fails. The idle speed actuator is responsible for regulating the engine speed when engine load changes while idle. Change in condition includes active air-conditioning and other onboard electrical components.

What causes the idle speed actuator to fail:

Two main issues we can highlight for your knowledge:

Contamination
Low or zero voltage supply from the engine management control unit

Symptoms of a failed idle speed actuator

Fluctuating idle speed
Engine stops running at idle speed

SMG (Sequential Manual Gearbox) Transmission – This component enables manual gear changes minus the manual clutch. The faults that result from a failed SMG cause trouble going through the gears, accompanied by SMG fault codes. A visit to your local repair shop may reveal a leaking SMG transmission that calls for an overhaul – of course at a steep price.

Valve cover gasket oil leak – Most BMW engines are prone to this problem and the problem is usually caused by cracks or wear and tear. You will experience a check engine light on the dashboard which is a warning on the depleted oil. The oil will also find its way into the engine block and a strong pungent smell of burning oil should alert you to this issue. Before the engine is damaged from running on depleted oil it is critical to resolving this issue as soon as it is detected.

The next worst BMW engine is the…

BMW Engines to avoid - N54 Twin turbo ENGINE

n54 in the Z4

This engine is found in the BMW X6 – E7, BMW 740i – F0, BMW 535i – E60, BMW 335i – E90, E91, E92, BMW 135i – E82/E88, BMW Z4 – E89.

BMW enthusiasts hail this engine as the direct competitor to the 2JZ and they praise this rig endlessly. In reality, however, it is one of the most unreliable BMW engines. Which eclipses the praises of enthusiasts..

The next most unreliable bmw engine is the…

N54 Common Problems

Fuel leaks at the injectors – When the injectors leak fuel, the fluid drips on the spark plugs, and the first symptom you witness is misfires and loss of engine power.

High-pressure pump failure – This pump feeds the injectors with fuel for combustion. It is prone to constant failure. Besides going into limp mode, you can catch symptoms of this problem from slow engine starts.

Turbochargers failing – If you spot white smoke coming from the exhaust, coupled with low to no boost at throttle – then your turbos are failing. The only solution is a replacement of the turbos.

Coolant leaks – Coolant leaks are caused by gasket leaks, water pump failure, or faulty radiators. In most cases, the dashboard should bring to your attention the rising engine temperature and if you check under the hood you might see coolant leaking. Check for all gaskets and ensure the seals are properly secure before replacing the coolant.

Water Pump Failure – At around 80,000 miles most BMW will need a water pump replacement. The water pump keeps the coolant flowing in the cooling system. High engine temperatures also indicate a failed water pump.

BMW Engines to avoid - DX5 ENGINE

dX5 engine in the X5

This is the diesel engine on the BMW X5. Diesel engines on luxury cars surface various issues. They are excellent workhorses only when maintained well. This BMW engine has a couple of problems including engine stalls. Besides that scary fault we have:-

Turbocharger failures – With lost power on the throttle, whining sound from the engine, and also white smoke from the exhaust you are moments away from failed turbos. The causes for turbo failure in this engine include lack of oil in the engine probably as a result of a leak. Also, low-quality oil destroys turbos. Wear and tear can also lead to turbo failures but at least you must be looking at 70,000+ on the odometer.

Clogged DPF (Diesel Particulate Filter) When this engine is not subjected to extended highway travel and instead used as a Mall crawler the DPF gets clogged and the service engine soon will light on the dash.

Other components that are prone to fail to include:

DPF FILTERS unplugging
Throttle body actuator
Cracked EGR cooler
EGR valves

You are most likely to encounter most of these problems in high-mileage units.

BMW Engines to avoid - N62 ENGINE

N62 in the 750Li

This engine is a naturally aspirated V8 engine created by BMW in 4.4L and 4.8L displacements. It powers the following BMW models:

545i, 645Ci 2004-2005
550i, 650i 2006-2010
X5 4.4i, X5 4.8iS 2003-2006
X5 4.8i 2007-2010
750i, 750Li 2006-2008
745i, 745Li 2002-2005

Unfortunately, it is also one of the most unreliable BMW engines. The number one fault in these engines is smoke in the engine compartment and exhaust. It is caused by leaking oil as a result of faulty valve guide seals. More significant problems are in the excess carbon build-up that leads to a residue that must be cleaned up otherwise your engine might seize.

BMW n62 engine problems

This engine has the following problems:

Valve stem seal failure
Coolant transfer pipe seal failure
Secondary air system failure

BMW Engines to avoid - N47 Inline 4 Engine

n47 IN THE f20

For an engine that is present in a majority of BMW engines, the torque from this engine powers among others the E90, E91, E81, E82, E88, F20, and F30 BMW variations. It provides a great driving experience.

However, the most glaring problem is the timing chain that stretches and eventually snaps. It can lead to catastrophic engine failure or outright engine stall. This can happen with the engine in idle mode or motion which means you can be cruising and the engine stalls suddenly.

Boost loss from a broken spring in the wastegate. It ultimately affects fuel consumption negatively.

Why are BMW engines so unreliable?

Let’s face it, the list of unreliable BMWs is quite something. But thanks to clever marketing, BMW still manages to sell thousands of cars.

To the uninitiated, the luxurious driving experience is shattered once the engines slap them with endless bills in repair.

But you should appreciate one key point – BMW is designed for the driver seeking comfort and performance. The trappings of comfort in BMW models are a facade to engines that need tender loving care.

You must be committed to a strict maintenance schedule and also have a standby fund to finance some repairs.

Why are BMWs so unreliable?

The main reason why BMW engines are so unreliable is not due to poor engine design. The auxiliary components – mostly electronic – make the motors complex and difficult to troubleshoot and hence they are the main cause of BMW’s unreliability.

The components are added to enhance performance and comfort. We are looking at – actuators, relays, and modules – that perform various functions. The combined complexity makes the vehicle difficult to troubleshoot and prone to constant glitches. It’s like operating and maintaining a NASA spaceship. Although engines can affect the performance of the vehicle, other parts also play a vital role. For example, if you don’t use good quality tires, it can reduce the efficiency of the engine. So, it’s always advisable to read reviews of the tires from a trusted platform like TireReviews.

We cannot dismiss the entire BMW catalog as unreliable but we can pick the specific models or BMW engines to avoid.

Wrapping up

BMW develops fantastic engines (see article below) but some flops are also credited to the German manufacturer. This is not an exhaustive list nonetheless but highlights the main culprits.

Most Reliable BMW Engines

In this article, we are going to delve into the most reliable BMW engines from years back – to date.

The Best BMW V8 engines

This isn’t just a list of the best BMW V8 engines but a deep dive into the Bavarian masterpieces over the years. Let’s rev those engines and feel the power!

Most reliable BMW X5 ENGINE

Find out the best pick for a reliable BMW X5 engine. Some BMW X5 engines are best avoided while others will serve you fine…

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