7 To-Be-Expected Mercedes M139 Engine Problems (45 AMG)

Twin-scroll turbos are something us petrol heads dreamt about having in our bug-eyed Subaru Impreza’s. Nowadays, you’ll find this exact technology hidden under the hood of some amazing AMG Mercedes-Benz models. Today we’re taking a closer look at the Mercedes M139 engine. This engine is best known for its badge name, the 45 AMG.

Doing your own homework and learning about the problems that you might come against is always a good idea. You just don’t want to leave things to chance and hope for the best. Those guys usually pay the hefty repair bills. Smart people research. And this is why we are here to help you out with you by pinpointing these issues for you.

First, we are going to learn more about the general specs of the M139 engine and see what kind of power this engine makes. Then, we are going to learn more about the common Mercedes M139 engine problems and see what troubles this engine. Lastly, we are going to cover the applications, so without further ado, let’s dive into the topic.

Basic Mercedes M139 Engine Specs

The M139 is a fairly new engine design. This engine was introduced in 2019 and is still in production.

This engine is based on the M260 engine. It features an inline-4 configuration with 2.0L of displacement.

What is worth noting is that this is a high-performance engine. It is not your typical four-banger. This engine has incredible performance that can outmatch even the big V8 engines that Mercedes uses.

And that was the whole purpose of this engine. The M139 replaced the V8 used in the C63 AMG. So, if we follow the same pattern, Mercedes should have called this model the C20 AMG. 

But that’s not how things go nowadays, unfortunately. Everyone wants to milk money on old glory. Just for input, the original C63 AMG was a 6.3L engine.

Nevertheless, the M139 is an excellent engine that implements some revolutionary technologies in order to make this amount of power.

The engine features an aluminum alloy block and aluminum alloy DOHC cylinder head with a Camtronic system for valve control. This system uses variable valve timing and variable time lift.

There is also a twin-scroll turbocharger for adding boost and creating power. Here are the full specs of this engine:

  • Configuration: inline-4
  • Displacement: 2.0L
  • Cylinder Bore: 83 mm
  • Piston Stroke: 92 mm
  • Block & Head Material: Aluminum Alloy
  • Cylinder Head Design: DOHC with 4 valves per cylinder
  • Variable Valve Timing: Yes, Camtronic
  • Compression Ratio: 9.0:1
  • Direct Injection: Yes
  • Turbocharger: Twin-Scroll Turbocharger
  • Power Output: 382 – 416 hp
  • Torque Output: 354 – 369 lb-ft (480 – 500 N-m)

Common Mercedes M139 Engine Problems

Common problems with the Mercedes M139 engine include:

  • Spark Plug & Ignition Coil Failures
  • Carbon Buildup
  • Potential Problem With The Valves
  • Injector Failures
  • Requires Quality Oil
  • Less Efficient
  • Expensive Maintenance

Now that we are familiarized with the M139 problems, we can further elaborate on these issues and learn how serious they are.

But to make a strong note, this engine is very much new, there are only a handful of these engines. There are no major design flaw reports with the M139. But there are some things that you need to take into concern. So, let’s cover them in detail.

Spark Plug & Ignition Coil Failures

Spark plug and ignition coil failures are expected problems for the M139 engine. This engine uses direct injection and this causes a lot of stress on these ignition components. To be fair, even the most reliable AMG engines, like the M113 or the M152 are not imune to these issues.

So, it is quite expected that you will have serious issues with misfiring and check engine light once the vehicle reaches 50,000 miles (ca. 80,467 km), or even sooner.

Direct injection is a blade with two sharp ends. You get a lot of benefits like lower emissions and reduced fuel consumption and you get many of these problems.

So, you have to prepare for these issues, especially if you purchase this engine on the second-hand market. Who knows how well the car was maintained by its previous owner?

Luckily, replacing these components is not that expensive. But it is more expensive when you compare Mercedes Benz with other car manufacturers. Benz parts are pretty pricey compared to lower-tier carmakers.

Carbon Buildup

Carbon buildup is one of the potential problems in this engine. This engine uses both direct and port injection.

This makes this engine to be rather safe from carbon but not completely safe. On many of the M260 engines that are closely connected with this engine, we have noted that there are problems with carbon debris buildup on the cylinder head from the inside of the combustion chamber, as well as on the piston crown.

This problem can cause the valves to fail and create issues like engine misfires, check engine light, loss of power, and so on. Not to mention that the injectors can also be clogged up with carbon and stop operating.

In addition to this, there can also be carbon buildup in the EGR valve. The EGR is the exhaust gas recirculation valve. Every modern engine has one of these valves that helps it redirect some of the exhaust gasses into the block to burn again.

Potential Problem With The Valves

Also, another problem that can damage the valves and cause cylinder head failure is the Camtronic system.

This is a system that Mercedes uses to regulate the work of the camshaft and adjust the variable valve timing, as well as the variable valve lift.

The valves are opening and closing at an alarming rate with this system. And this caused cylinder head failures on the M260

The valve guides wear out and fail, which causes the valve to wobble around and this will make the valve not seal properly.

If you don’t have a proper seal of the valve, this will result in a check engine light, loss of power, and engine misfires.

This problem often requires cylinder head replacement since these cars are still under warranty. And it is cheaper for them to replace the head than refurbish it.

Let’s now move to the next Mercedes M139 engine problems.

Injector Failures

Injector failures are also a common problem in direct injection engines. These injectors are really sensitive to fuel.

So, you shouldn’t add fuel that is not recommended for this engine. Since this engine is high-performance, it should always run on premium gas.

Not to mention that these injectors have a much bigger failure rate than your regular port injectors. And this engine runs both port and direct injection.

Usually, when injectors fail, they can start to leak or can clog up. In this case, only replacement is the viable option if you want to return the engine back to normal working order.

Requires Quality Oil

Another thing that you need to take into concern is that this engine requires quality fully synthetic oil. You just cannot add any type of oil to the M139 engine.

This is a high-performance engine and you should use oil that is graded specifically for the Mercedes standard and also oil that has the exact viscosity that is prescribed by the factory.

This is essential because your engine can suffer from higher wear on the internals, high or low oil pressure, and also the oil pump can fail if the viscosity is messed up. So, beware of this if you become an owner of a car with this type of engine.

Less Efficient Than Expected

Many people are thinking that they will buy a four-banger and the engine will be as fuel efficient as a Toyota hybrid.

But this is not the case, this engine will drink a lot of fuel. It might be 10-20% more efficient than its V8 predecessor. But remember one thing, this is a high-performance engine. It is designed for power.

So, you get power but you also get more frequent visits at the gas station. This is why if you want to get a more efficient vehicle, this engine is not for you.

Expensive Maintenance

Another thing that you need to take into concern and something that can also be a problem with the M139 is the expensive maintenance.

This engine, even though small, is a work of art. Very complex in its operation, the turbo system is also really complex, and as a whole, the engine repairs will cost you a good penny.

Not to mention that this is still a Mercedes-Benz and this is pretty understandable.

Which Cars Have The Mercedes M193 Engine?

258 kW Model

  • 2019 –  Present Mercedes AMG CLA 45
  • 2019 –  Present Mercedes AMG A46
  • 2020 –  Present Mercedes AMG GLA 45
  • 2022 –  Present Mercedes AMG SL 43
  • 2022 –  Present Lotus Emira

300 kW Model

  • 2022 –  Present Mercedes AMG C43

310 kW Model

  • 2019 –  Present Mercedes AMG CLA 45 S
  • 2019 –  Present Mercedes AMG A45 S
  • 2020 –  Present Mercedes GLA 45 S

350 kW Model (M139L)

  • 2022 –  Present Mercedes AMG C63 S


What are the Mercedes M139 Engine Problems?

This engine does not have any problems reported on it yet, there are still some things that you should take into concern like the direct injection system and turbocharger, as well as the cylinder head failures that occur on the M260, the closest sibling of this engine.

Is the Mercedes M139 Engine Reliable?

Yes, as of now, this engine is pretty good. There are no serious faults reported on it. But that doesn’t mean that there will be no issues in the future. This engine is only a few years old and problems often appear after 5 to 10 years of operation.

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