7 Common Mercedes M152 AMG Engine Problems (SLK55 AMG)

The SLK Mercedes is like a two-edged sword, it’s both amazing and certain people love it, but on the other side it’s always going to live in the SL’s shadow, much like the Porsche Boxster will in the 911’s shadow.

We love the SLK because it’s a much more sensible choice for performance on the budget. Not only is it cheaper to maintain (due to a lack of things like the Mercedes ABC suspension), it’s also cheaper to buy in the first place.

Doing your own research is mandatory when it comes to buying a used model, especially when it comes to AMG cars. AMG cars can be crazy expensive to purchase, as well as to maintain in the long run. So, making the right call is the key if you don’t want to end up in an endless money pit full of problems. That’s why we are here to help you out by pinpointing these problems for you.

First, we are going to learn more about the specs of the engine and then we will dive into the Mercedes M152 AMG engine problems. We will list all of the problems and cover them in detail. Lastly, we will learn more about the models that have this engine. So, let’s get started.

Basic Mercedes M152 AMG Engine Specs

Now, before we dive into the problems of the Mercedes Benz M152 engine, let’s first learn more about the basic specs of this engine. Specs are really important to know before you decide to purchase a vehicle with an engine of a certain type. So, let’s cover the specs.

The M152 engine is a V8 naturally aspirated engine that was produced between 2012 and 2015 by Mercedes-Benz.

This engine, although it carries a different engine code, in general it is the same engine as the M157 AMG. But the difference between the two is that the M152 is naturally aspirated, while the M157 is (or can be, for a lack of better words) turbocharged.

In addition to this, the M152 was also a little revised by AMG and includes some upgrades that make it perform as a proper high-performance engine.

The engine block of the M152 is made out of aluminum alloy, similar to the cylinder heads. Having an all-aluminum design makes this engine extremely lightweight.

The head design is a double overhead camshaft layout and there are four valves per cylinder. In total, this engine has 32 valves.

This engine implements a lot of upgrades like direct injection and cylinder deactivation. Making it extremely efficient.

But here are the full specs of the M152 engine.

  • Engine Configuration: V8
  • Displacement: 5.5L
  • Bore: 98 mm
  • Stroke: 90.5 mm
  • Block & Head Material: Aluminum Alloy
  • Head Design: DOHC, 4 valves per cylinder
  • Direct Injection: Yes
  • Compression Ratio: 12.6:1
  • Horsepower: 416 hp (310 kW)
  • Torque: 540 N-m (398 lb-ft)

Common Mercedes M152 AMG Engine Problems

Common problems with the M152 engine by Mercedes-Benz include:

  • Spark Plug & Coil Failures
  • Stretched Timing Chain
  • Injector Failures
  • Carbon Buildup
  • Oil Leaks
  • from timing cover
  • Coolant Leaks

We listed the problems, now let’s move on and learn more about them in detail. Since this engine is pretty similar to the M157 engine, it shares many of the problems.

So, we can say that these issues are pretty much interchangeable. However, we couldn’t find evidence of cylinder scarring on the M152, which is a very big problem on the M157 engine. So, since there are no reports on this issue, the M152 is probably free from this typical Mercedes engine problem. Now let’s dive into the rest of the issues.

Spark Plug & Coil Failures

Let’s start with the first issue and this is probably the most common problem that plagues all of the modern Mercedes V8 engines. This is the spark plug and coil failures.

Ignition problems are so many on these Mercedes Benz engines and driving without a check engine light can be described as a miracle.

These components fail at an exponential rate, especially if you don’t drive the car very often or if these components were not replaced recently. But also, even in some new cars, these components tend to fail quite often.

Whenever you have a bad spark plug or coil, you will get a check engine light, there will also be engine misfires, rough engine idle, poor fuel economy, and low engine power.

The solution is simple, and that will require replacement of the faulty components. And you can only do this with an OBD2 scanner.

With this scanner, you will be able to scan the car for codes and if there are codes connected to an engine misfire on some of the cylinders, you know where to look for the problem. Then swap out the components and if the misfire repeats on the next cylinder you know which components are faulty.

Stretched Timing Chain

The next common problem on these M152 engines is the timing chain stretching that often happens when the engine gets a lot of miles.

The timing chain is the chain that drives the engine. It makes the bottom and top of the engine work together and also keeps the timing in check.

What can happen is that these chains tend to have issues, whether with the tensioners, that can lose tension and allow slack to develop. Or like in this case with the M152 engine where you have timing chain stretching.

This means that the chain becomes longer and this increase in length allows slack to develop. This could cause the chain to jump and you will lose timing.

If you lose timing, the valves and pistons can collide and your valves will get tweaked. This will result in thousands of dollars in repairs because the cylinder heads have to be refreshed and the timing chain replaced.

That’s why if you notice rattling noises, it is important to replace the timing chain and avoid further issues.

Injector Failures

Injector failures are also very common on these engines. This is the case because these M152 engines are using a direct injection system.

This is a completely new method of injecting fuel that is extremely good but it is also extremely bad at the same time.

The injection of fuel is perfect because gas is injected at high pressures that atomize the gasoline. But it is bad because there are special injectors for this system, as well as a secondary high-pressure fuel pump.

The high-pressure fuel pump on this engine can also break down. However, the most prevalent problem is the injector failure.

There are 8 of these injectors on this engine and all of them will fail once the engine reaches higher mileage. There will be check engine light, poor engine work, engine stalling, and difficulty starting.

The solution is to replace the faulty injectors or replace all of them if you have the budget.

Now let’s move on to the next Mercedes M152 engine problems.

Carbon Buildup

Carbon buildup is another problem that is greatly attributed to the direct injection system. So, why is this the case?

Well, this is the case because direct injection uses a different way of injecting fuel. The injector basically sits on top of the cylinder.

Unlike in MPI engines where injectors are installed on the intake ports. Fuel is basically injected through the intake ports.

So, the intake valves are not washed by the gas in these direct injection engines since gas goes through a different place.

The oil vapors are accumulating on the intake valves and create a crust that over time can prevent the valves from opening and closing. That’s why it is recommended that you walnut blast the intake ports every 60,000 to 80,000 miles in order to be on the safe side.

Oil Leaks

Oil leaks are a problem that troubles almost every engine out there and the M152 engine is no exception to this rule.

Oil leaks can come from a variety of places like the front and rear main seals, oil pan, and valve covers.

But the most common place for this engine to leak oil is the timing cover gaskets. The timing cover gaskets are the gaskets that are placed between the timing cover and the engine block.

These gaskets allow oil to seep out from the engine and if the leak is serious, you can lose a ton of oil. That’s why it is advisable that you fix it immediately.

Now let’s move on to the next Mercedes M152 engine problems.

Coolant Leaks

And the last problem with this engine are the coolant leaks. Coolant leaks can happen from various places as well.

These coolant leaks can come from the water pump, upper and lower radiator hoses, as well as radiator hose fittings.

The important thing is to detect this problem on time because if the engine overheats, there could be some extremely expensive repairs. The engine could blow a head gasket and then you will also have to resurface the cylinder heads.

Which Models Have The Mercedes M152 AMG Engine?

  • 2012 – 2015 Mercedes Benz SLK 55 AMG


What Are The Problems With The Mercedes M152 Engine?

Common problems with the M152 engine include issues with the ignition components. So, problems with the spark plugs and coils are very common. Also, there is carbon buildup on the intake ports, oil leaks from the timing cover, coolant leaks, and timing chain rattle, and the timing chain tends to stretch and rattle at higher miles.

Is The Mercedes M152 Engine Reliable?

In general, this is a fairly reliable engine. It has a fair share of issues but the overall package is good. But the maintenance in the long run can be expensive if you only rely on mechanics to do the work. Many of these small issues can cost you thousands of dollars to fix.

About The Author