The Ultimate Guide to Mercedes Engine Problems (Diesel & Gas)

It’s no secret that the team here at Life On Four loves Mercedes-Benz vehicles, in fact, two of our team members, including me, drive the stars from Stuttgart. Having actual experiences with these vehicles and various Mercedes engines allows us to provide you with reliable information about these cars and all the Mercedes engine problems.

We’ve made it our goal at the beginning of 2023 that we shall become the number one resource on Mercedes engine issues here at Life On Four. And by the time of writing this, we have concluded 16 detailed reviews of several Mercedes engines.

Before we get into those engine problems, we want to first show you how our process looks like and why our information can be trusted. Ready to get started? Let’s dive right in!

How We Review Engine Problems of Mercedes Cars

One of the things that makes us different is the fact that we don’t just write up these reviews out of thin air. We have a process in place that assures us we get hands-on information about each engine. Here is how that process looks.

  1. We decide on the engine we’re going to review
    A lot of people write to us asking about engine problems of particular Mercedes models. If there’s enough requests, we pick that engine and start our research.
  2. We start gathering information online.
    Owners forums, Reddit threads and past research serve us as basis. You can learn a lot on owners forums but the information is scattered, and you have to spend hours compiling reliable information.
  3. We contact independent mechanics, Mercedes dealerships and owners in our area.
    Talking to people that have hands-on experience is what makes us different. By now, we have formed relationships with mechanics that always provide us with first-hand information to determine how serious and costly some of the engine problems we identify are.
  4. We write up our easy to understand and read engine problem articles!
    That is it! The majority of our time is taken up by research, once we gather the data, we do our best to provide you with guides that are easy to understand even if you aren’t that tech-savvy.

Mercedes Engine’s We’ve Reviewed in Detail

We’ve started compiling our ultimate guide to Mercedes engine problems by reviewing the problems of some of the most popular diesel and gas engines. We are constantly working on adding new models, but it’s not as simple as it may seem. Not only that, but we will update this page regularly as we review new engines every month!

Here are all the engines we have reviewed so far!

Gas Engines

Mercedes-Benz M278 Engine – V8 – 450,500, 550 (2010-2020)

The M278 is considered to be quite reliable, especially if you take into consideration the complexity of this engine. Modern V8 engine have to implement a number of complex systems to ensure the compliance with strict modern emissions systems. A well maintained M278 is a joy to drive, however, there are several important problems you need to be aware off.

Interested in this engine? Then make sure you don’t skip our full analysis of M278’s problems.

Most concerning problems:

  • Timing chain tensioner issues
  • Cam adjuster problems
  • Oil leaks contaminating the engine wiring harness

Mercedes-Benz M276 Engine – 300, 350, 400 (2010-2017 V6)

Introduced in 2010, this V6 gasoline engine was a popular choice for everyone seeking great power and better fuel efficiency than the V8 engine. It was present in the following Mercedes models: E300, E400, S350, S400, GLE, GLK, SLK and more.

It is considered to be a highly reliable engine, if you’re interested in learning more, read our full review of the M276 engine problems.

Most concerning problems:

  • Timing chain tensioner issues
  • Cam adjuster problems
  • Oil leaks contaminating the engine wiring harness

Mercedes-Benz M157 Engine – 63 AMG V8 (2012 – 2019)

The M157 is essentially the AMG version of the reliable M278 V8 engine. We would have no problems buying either of them, but you have to keep in mind that there are issues that can be very expensive to fix. This engine is found in 2012 – 2019 AMG models: E63, S63, CL63, CLS63, GLE63 AMG and many others.

If you want to learn more about the problems and applications of this engine, visit our blog post about all the M157 engine problems.

Most concerning problems:

  • Cylinder scoring (very serious)
  • Pre-2013 Timing chain problems
  • Various oil leaks

Mercedes-Benz M119 Engine – V8 – 400, 420, 500, E60 AMG (1990s)

The Mercedes M119 engine is undoubtedly one of the greatest V8 engines ever. Things were simply done differently in the 1990s and the M119 is the best example of German overengineering. Buying this engine after 30 years since it’s release is still a good idea, but there are some issues you need to be prepared for.

If you want a classic V8 Mercedes engine, you should definitely read our guide on all the problems of this Mercedes V8 Hall of Famer.

Most concerning problems:

  • Timing chain guide deterioration
  • Hardened vacuum lines
  • Exhaust lifter knock & plastic oil guide problems

Mercedes-Benz M112 Engine – V6 – 240, 280, 320, 350, 32 AMG

The M112 engine is a popular choice for all buyers of 1996-2008 Mercedes vehicles. This engine enjoyed a long production run and rightfully so, it was a reliable unit that many owners loved. It was featured in nearly all Mercedes passenger vehicles during that era.

Want to know more? You’re more than welcome to read our full guide on the M112’s engine problems.

Most concerning problems:

  • Disintegrating crankshaft pulley
  • O-Ring seal failures, causing engine oil to mix with engine coolant
  • Coil pack failures

Mercedes-Benz M113 Engine – V8 – 55 AMG, 430, 500 (1997-2008)

The M113 Mercedes engine is one of the most legendary performance engines ever. If you can find one in good condition, you should buy it on the spot. We’re serious, it’s just so good. You can find the M113 engine in Mercedes cars with the 55 AMG, 430 or 500 badge made from 1997 to 2008.

To get more information, we’ve prepared a blog posts that reveals all the potential issues of the M113 engine. Go read it!

Most concerning problems:

  • Kompressor intercooler pump failure on the M113 K engine variant
  • Rear main seal deterioration
  • Lack of oil pressure sensor

Diesel Engines

Mercedes-Benz OM656 Engine – 6 Cylinder – 350d, 400d

Mercedes-Benz’s latest flagship diesel is dubbed the OM656. Featuring an inline 6-cylinder configuration, this clean diesel engine is set to continue the great Mercedes diesel lineage. You’ll find this engine in numerous Mercedes models, including the W222 and W223 S-Class.

To see all the problems and the models that carry this engine, you have to read our full overview of the OM656 diesel engine.

Most concerning problems:

  • Vacuum pump failure
  • Rocker arms bearing failure
  • Ad Blue system problems

Mercedes-Benz OM654 Engine – 4 Cylinder – 200d, 220d, 300d

The OM654 engine is the smaller brother of the OM656 engine, featuring just 4 cylinder, this smaller diesel engines have replaced the older OM642 engine and by featuring a twin turbo configuration, matched both the power of its predecessor and halved the fuel consumption at the same time.

But did they come with the same level of reliability, read our guide to all the OM654 engine problems to find out!

Most concerning problems:

  • Rocker Bearings and Hydraulic Tappet failures
  • Carbon Buildup
  • Timing chain failures

Mercedes-Benz OM648 Engine – Inline 6 Cylinder – 320CDI, 280CDI

The OM648 engine is an inline 6-cylinder engine, born in the early 2000s which is considered to be the golden era of Mercedes diesel engines. The OM648 is widely recognized as one of the best Mercedes diesel engines ever made. It was featured in the pre-facelift version of the W211 E-Class and in the facelift version of the W220 S-Class.

Read our full Mercedes-Benz OM648 Engine Problems article to learn more.

Most concerning problems:

  • Problems revolving around carbon buildup
  • Fuel injector washer deterioration and “Black Death”

Mercedes-Benz OM646 Engine – 200CDI, 220CDI (2002-2010)

We had a real good time writing about this engine, one of our team member’s has owned a W204 C-Class Mercedes with this engine for several years now and has now done over 170,000 miles (ca. 273,588 km) without a single major problem. This 2.1L, 200CDI and 220CDI dubbed engine is a true work horse.

But just like any engine in existence, the OM646 comes with a set of problems.

Most concerning problems:

  • Deterioration of the intake manifold swirl flaps
  • Leaky fuel injector copper washers
  • Balancer shaft problems

Mercedes-Benz OM612 Engine – 2.7 L 270CDI (1999-2006)

The controversial 270CDI engine, also known as the OM612, always divided the Mercedes diesel communities. A big part of owners swear by this engine, and the other half reports of numerous problems. We would still describe this engine as a reliable diesel work horse and we have done our research to back up those claims.

If you’re interested in this engine, we suggest you head straight to our full review of the OM612 diesel engine.

Most concerning problems:

  • Engine wiring harness problems
  • Intake manifold swirl flap problems
  • EGR valve problems

Mercedes-Benz OM642 Engine – 3.0 V6 – 320CDI, 280CDI

I currently own a W211 E-Class wagon with the OM642 3.0 CDI diesel engine. After spending over $4000 on the maintenance of this engine, I can say that I know this engine in and out. Don’t get me wrong, it’s an incredible engine, but as much as it is amazing to drive, it’s also complicated to maintain.

We have a very popular article posted on all the engine problems of the OM642 and also my experience with fuel dilution with this engine.

Most concerning problems:

  • Oil cooler leaks at the bottom of the V6 valley
  • Timing chain and timing chain tensioner failure
  • Turbo actuator failure and turbocharger inlet seal failure

Mercedes-Benz OM651 Engine

We have no problem saying that the OM651 is perhaps one of the best modern Mercedes diesel engines ever. Sure it has its issues, but as many mechanics would tell you, it is no surprise that so many of these engines are doing 500,000 kilometers and more without major issues. If you find a car with this engine that you like, just be sure that the service history is impeccable!

If you want to learn more about this great Mercedes diesel engine, consult our full guide to the OM651 engine.

Most concerning problems:

  • Timing chain and timing chain tensioner problems
  • Ad Blue problems on newer BlueTec models
  • Coolant leaks

Common Mercedes Engine Problems

There’s a lot of article online that just list common Mercedes engine problems, but that hardly makes any sense. Sure, every engine will eventually experience oil leaks, coolant leaks and general issues like that. But that’s hardly of any help to any Mercedes owner out there. That is exactly why we focus on each engine separately (we just listed them above).

However, we still believe we can provide you with a better list of common Mercedes engine problems than most of our competitors.

Common Mercedes engine problems include:

  • Timing chain and timing chain tensioner related issues
  • Carbon buildup on all direct fuel injection engines (diesel and gas)
  • Intake manifold swirl flap deterioration and problems
  • Fuel injector copper washer failure on diesel engines
  • Various oil leaks
  • Turbocharger problems
  • Camshaft adjuster problems
  • Cylinder scoring

It is important to note that not all Mercedes engines will encounter these issues, please consult our dedicated engine problem guides to see the full list of problems of each engine. Another thing that is important to realize is the face that the majority of these problems can be prevented by sticking to the regular maintenance intervals and adopting a mindset of meticulous care.

People that like to blurt out “Mercedes engines are unreliable”, often don’t have a single clue about the complexity of these engines and the care that they need. And we’re not talking that all these engines need to be “babied” but it helps to know what causes some of these known issues and how your driving style and maintenance can prevent them.

How To Avoid Engine Problems With Your Benz

Avoiding engine problems with your Mercedes-Benz is done in the exact same way as it is done with any other engine. Yes, it’s true that come issues that are caused due to poor manufacturing or design from the factory cannot be prevented. However, the majority of those concerns are usually taken care of through recalls or technical service bulletins. All other problems however can be prevented by the correct use and maintenance of the engine.

Here are is how to avoid Mercedes-Benz engine problems:

  • Respect the manufacturers maintenance guidelines
  • Learn how to operate your engine
  • Get to know the common problems of your engine and practice preventive maintenance
  • Learn how to keep an eye out on your engine oil
  • Observe the behaviour of your engine
  • Observe the engine and around the engine for any engine oil or coolant leaks

Regular maintenance & maintenance history

The number one reason you see problems with Mercedes engine is because not many people make it their mission to keep up with the regular maintenance schedule. Simple oil and filter changes work wonders for the longevity of the engine, but the truth is, many people tend to forget about the basics.

We recommend having regular oil and filter changes every 10,000 miles (ca. 16,093 km) or once every single year. Even if you don’t do that many miles per year, you should replace your engine oil due the time sensitive degradation of the oil. Without high quality oil and appropriate lubrication of the engine’s moving parts, you’ll surely face some unwanted problems.

Learn how to operate your engine

We have recently written an entire guide on how to drive a car with a diesel engine. And the majority of those lessons can be translated onto all Mercedes engine.

Here is what you should be doing when driving your Mercedes:

  • Give the car the time to warm up to it’s working temperature
  • Avoid doing short trips only, especially with direct fuel injection engines
  • Do not drive on minimum fuel levels all the time
  • Avoid prolonged idling
  • Allow your engine a minute to cool down before you turn it off

Take the time to learn

If you’re just buying your Mercedes-Benz, you should take an hour to do a Google search about the engine that is in your desired Benz. Or better yet, you can use the search function on our website to find all the issues you should know about.

A simple research about the engine will usually reveal any problems that you should be aware of prior to purchasing your Mercedes-Benz. Based on the information you find, you can either step away from the purchase or use that knowledge to ask the seller if the issues have been taken care off. If they haven’t been, you also have a good basis for the final price negotiation.

Inspect engine oil levels

Inspecting your engine oil levels only takes a minute each week, but it can save you thousands in maintenance costs if you happen to detect any issues before they develop into full scale catastrophes. We have prepared a detailed guide on how to check your engine oil levels. The majority of Mercedes cars have sensors that detect engine oil levels, consult your owner’s manual to see how you check the engine oil level on your dashboard.

Based on your readings, you can detect if the car is excessively burning engine oil or if you have a problem with fuel dilution and rising engine oil levels.

Observe the behavior of your engine

Your engine is constantly telling you things, all you need to do is listen. We get it, this sounds weird but it’s not far from the truth. Engine problems can manifest in many ways. They can start with weird noises or weird behavior such as prolonged idling, misfiring, poor responsiveness, excessive exhaust smoke, excessive engine vibration and more.

It’s up to you as the driver to keep an eye out for those things and to take action as soon as you notice anything out of the ordinary. The majority of Mercedes engine problem are much easier and cheaper to fix if they are caught at the early stages. Never ignore warning signs!

Keep an eye out for engine oil leaks and coolant leaks

The majority of us park our cars in the same location over and over again. When you move out from your parking space, keep an eye out for any oil or coolant leaks. Oil and coolant look and smell completely different, so you shouldn’t have problems figuring out what exactly is leaking.

Another thing that we recommend every Mercedes owner do is to use their smartphones flashlight and inspect your engine and cooling system for any leaks. You should inspect all parts of the engine, see if there is any oil seeping out or if there is any coolant leaking from the radiator or any of the coolant hose joints.

Modern cars, especially Mercedes, all come with engine splash shield, which is why you are more likely to see an oil stain at the bottom of the engine than on your driveway. Taking the time to shine a light around the engine can really help you detect some developing engine problems.

Which Mercedes Engine is Most Reliable?

If we had to answer this question truthfully, we would easily list any of the Mercedes engine made in the 1980s or 1990s as the most reliable.

In our opinion, the most reliable Mercedes engines are:

  • The Mercedes M104 inline 6 cylinder engine
  • The Mercedes OM617 diesel engine

These 2 are definitely our favorites when we only consider reliability. Both of these engines are known to run for a couple hundred thousand miles before needing a rebuild. Both are older engines, with the M104 being an icon of the 1990s and the OM617 being the reason so many people love Mercedes diesel engines today.

Are modern Mercedes engines reliable?

Sure they are, it’s just hard to compare them to the older, much simpler engines due to the fact that modern Mercedes engines can never be as simple as engines once were. And that simplicity is what kept that Mercedes reliability status alive and well.

Both modern diesel and petrol Mercedes engines are incredibly complex for two reasons:

  • To deliver the immense power we all love
  • To comply with the strict environmental policies

These two reasons alone make modern Mercedes engines less reliable because in order to achieve high power and low CO2 emissions (khm, khm AdBlue problems), the engines became much more complex, and they are pushed to work under higher compression. This leads to lower long-term reliability and higher maintenance costs.

However, we are not saying that modern Mercedes engines aren’t built to last. They are, especially when they are maintained regularly.

Which Mercedes Engine Should You Avoid?

Let us give you a quick tip: Avoid early model years of any Mercedes engine, just to stay safe.

We could easily list the M126, the M272/273 and the OM642 or even the OM651 as one of the worst and least reliable Mercedes engines ever. And yeah it’s true, all of these engines did have major engine problems when they were first released, and I’m sure many owners lost plenty of nights of good sleep over them. But if there’s one thing that Mercedes does, it’s that they fix their mistakes quite fast.

Nowadays, we would not have any problems buying any of those engines if they had a documented maintenance history. The lesson here is, don’t be the first in line that buys a new Mercedes with a new engine. Stick to engines that are tried and proven. That is not always possible if you’re in the market for a new Mercedes, but then again, you probably aren’t that concerned about engine problems if you can afford a new Benz

P.S.: The Mercedes extended warranty program might be expensive, but it’s worth it, trust us!


We want to end this page by pointing out something incredibly important, especially for those that are in the market for a used Mercedes-Benz. Maintenance history is the number one most significant factor for long term reliability of any Mercedes-Benz engine you can buy.

We are being more than serious here. If you’re buying a Mercedes and the first thing you notice is missing maintenance history or obviously fake records of maintenance, just walk away, don’t go for a test drive, don’t fall in love with the car, just run.

You don’t want to be the poor soul that will pay for all the sins of the past owners out of your own pocket. I’ve been there, and I’d rather buy a new Mitsubishi Mirage than suffer through that experience again. Keep this in mind and good luck!