Mercedes M276 Engine Problems (V6 Petrol – 300, 400, 43 AMG)

We’ve recently talked about the V8 M278 engine problems here on Life On Four, and we think it’s only fair we take a closer look at his smaller V6 brother, the Mercedes M276 engine. The M276 engine is a successor to the M272 engine. It replaced it in 2010 and immediately became a popular option among Mercedes enthusiasts.

This article dives deep into all the common Mercedes M276 engine problems and concerns. If you’re in the market for an M276 powered Benz, consider this essential literature.

Basic M276 Engine Specifications

The M276 engine is a 3.5L V6 engine with:

  • An aluminum engine block (with Nanoslide cylinder coating)
  • Dual overhead camshafts
  • Variable valve timing
  • 2-stage valve timing chain design
  • Direct injection piezo-electric fuel injectors

In terms of power and turbocharger configuration, there were three engine variants:

M276 DE 35

This is the naturally aspirated version, meaning it has no turbochargers. There were three sub-variants, each introduced with a different model year and model. The weakest, detuned version was featured in the C300, S300 and E300 models from 2013 to 2015. It produced 185 kW – 248 horsepower and 251 lb ft – 340 Nm of torque.

The first variant of the DE 35 engine was features in the 2011 C350 BlueEfficiency C-Class. It produced 215 kW – 288 horsepower and 269 lb ft – 365 Nm of torque.

The only variant left was the one featured on 2011-2015 350 badge models. This version produced 225 kW – 306 horsepower and 273 lb ft – 370 Nm of torque.

M276 DE 30 LA

We’ve entered the forced air injection area. All variants of the DE 30 LA M276 engine feature twin IHI turbochargers. Note: this is the only M276 engine version with a smaller, 3.0L displacement. The first variant produced 245 kW – 329 horsepower and 480 Nm – 354 lb ft of torque. It first appeared with the 2014 model year W205 C-Class C400 and other models such as the E400, GLE400, E450, S450 and S500e.

The second variant appeared in 2015-2016 with greater performance figures. This version produced 270 kW – 362 horsepower and 521 Nm – 384 lb ft of torque. This version was avaliable in the 43 AMG and 450 badge Mercedes cars.

The last version, introduced in 2019 produced 287 kW – 385 horsepower and 521 Nm – 384 lb ft of torque. It was featured in the S580e and the 2019+ W213 E-Class E450.

M276 DE 35 LA

The DE35 LA version of the M276 engine is essentially the same as the naturally aspirated DE35 version. Similarly to the DE30 LA version we just described, it features a twin IHI turbochargers (different type) but it’s running on lower boost. According to Wikipedia, the bigger displacement and a lower boost, this version offered better fuel economy. It was featured in the 2015-2018 S400, E400, CLS 400 and several other models.

mercedes m276 engine image
M276 engine bay

Common Mercedes M276 Engine Problems

Before we get into all the problems, it’s important to note that the majority of problems we list here are shared with the bigger M278 V8 engine. We are not simply repeating the same problems, this comes as a consequence of the face that the engines are almost the same, with the M276 simply having 2 cylinders less.

If you’re rushing, here’s a quick list of M276 engine issues. We’ll describe each of the concerns as we continue.

Common M276 engine problems include:

  • Timing chain tensioner failure
  • Cam adjuster problems
  • Engine wiring harness oil leaks
  • Oil leaks
  • PCV valve failure
  • High pressure fuel pump failure
  • Carbon build up
  • Other problems

M276 Timing chain tensioner rattling noise

This common issue is present on both the M278 engine and it’s little brother the M276. A rattling noise that can be heard at cold start up is caused by a lack of oil pressure in the secondary timing chain tensioner. As the engine eventually builds up the missing oil pressure to the timing chains, the rattling noise disappears.

According to the LI05.10-P-056435 Mercedes Xentry Bulletin, the issue is resolved by installing non-return check valves by inserting them into the tensioner oil supply opening on both sides of the cylinder head. Both left and right secondary timing chain tensioners need to be replaced as well.

💡 This is a well known problem, if you’re buying a used M276 powered Mercedes we recommend having it checked out before the purchase.

Check the service bulletin we linked above to see the engine codes that are affected.

Mercedes M276 Cam adjuster failure

This issue is not the most common, but if you do a quick Google search for “M276 camshaft adjuster problems” you’ll see a number of videos and owner’s forum threads dealing with these issues. So it is common enough for us to mention it.

Being a critical part of the engine’s variable valve timing system, it’s easy to understand why premature wear of the camshaft adjuster can lead to problems. The first symptom of this problem is engine rattling at cold start-ups. We don’t have a recording of the sounds worn out camshaft adjusters make, but it is significantly different compared to the noise from the secondary timing chains we just mentioned.

An experienced mechanic will easily differentiate the sounds and the origin of the sounds. In any case, if you ignore this issue, a number of diagnostic trouble codes and misfiring will eventually start occurring.

Engine wiring harness oil leaks

The title of this problem might sounds weird, but it makes sense. Kind of. Due to an oil leak at the camshaft position sensors and camshaft magnets, the engine wiring harness, that is sitting right below the source of this leak, can get contaminated with oil.

This doesn’t sound like much of a problem, but it can be. The acidity of oil break down the wire coatings, causing all kinds of electrical problems, but even more common than that, the oil on the engine wiring harness can slowly make its way towards other electronic components and causing a havoc once it comes there.

Keep this issue in mind and take care of it as soon as possible!

Oil leaks

Oil leaks are nothing that we consider out of the ordinary, every engine will eventually leak oil once it racks up the miles and the time does its thing on all the plastic and rubber gaskets.

To make things easier for their mechanics, Mercedes released a technical service bulletin on oil leaks that are common on both the M276 engine and his bigger V8 brother.

Common M276 engine oil leaks include:

  • Area of the timing case cover
  • Area of water pump
  • Area of coolant thermostat
  • Area of oil pan
  • Other sealed surfaces

According to Mercedes, there are various reasons for this, but none of the issues is considered to be major.

PCV valve failure

A PCV or a crankcase breather valve is an essential component of any modern inner combustion engine. This relatively cheap component is designed to capture the gasses produced by the crankcase and route them back into the combustion chamber to be burnt off.

A failed PCV valve can cause a havoc in the engine. It can cause misfiring, poor idling performance, but most importantly it can dirty up your engine with oily sludge that would otherwise get burnt up in the combustion chamber.

You can see where the PCV valve is located in the M276 engine, how to replace it and which part numbers are needed for a replacement in this Mercedes PDF.

High pressure fuel pump failure

Direct injection engine, like the M276, require a constant stream of highly compressed fuel delivered directly to the fuel injectors. The component responsible for this job is the high pressure fuel pump. As it fails, the engine can no longer deliver fuel directly to the combustion chamber with enough pressure.

This leads to stalling, erratic engine behavior, or even the inability to start once it fails completely. Refer to this official guide on high pressure fuel pump replacement for more information on the process and required parts.

The YouTube video we posted above in the PCV valve failure section also does a good job displaying how to access the high pressure fuel pump on the M276 engine.

Carbon build up

Like all direct injection engine, the M276 is also prone to experiencing problems with carbon deposits. To make sure this doesn’t happen, we’ve prepared a detailed guide on engine carbon deposits, which includes the measures you can take to prevent this nasty issue.

Which Cars Have the M276 Engine?

Mercedes-Benz’s M276 V6 engine can be found in the following cars:

  • W221 S-Class S350
  • W222 S-Class S400 Hybrid
  • W212 E-Class E300 – E400 Hybrid
  • W213 E-Class
  • W218 CLS 350
  • W204 C-Class C350 – C300
  • W205 C-Class
  • W166 ML (GLE) 350
  • X204 GLK 350
  • W251 R-Class 350
  • R172 SLK 350

For the full list divided per engine type, please visit the M276 Engine Wiki.

Conclusion

The Mercedes M276 engine is one of our favorite modern V6 petrol engines. Sure, the M278 is more exciting, and it sounds better due to a V8 configuration, but the M276 just makes more sense for those seeking better fuel economy, less expensive maintenance and better reliability. The M276 is a perfect combination of power, efficiency, and reason.

If you’re looking more to learn more, read our ultimate guide to Mercedes engine problems!

Frequently Asked Questions

Is the Mercedes M276 engine reliable?

Yes, we would say that a well maintained M276 engine is definitely a reliable engine. While it is true that it does suffer from a few minor problems, none of them would deter us from buying this engine.

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