The Mercedes M156 Engine Manual. The Mercedes-AMG M156 engine has a solid reputation for being one of the company’s best-built production engines. It is a naturally aspirated V8 that first appeared on the market for the 2006 model year. It was also Mercedes and AMG’s penultimate normally aspirated V8, making the M156 engine a true piece of racing history.
The engine is well-known for its flawless design and exceptional performance. It had a maximum power range of 451-518hp and could easily do a 0-60 sprint in under 4 seconds. AMG worked heavily on the M156 to build a distinct, powerful V8, which is unlike any other Mercedes engine. Furthermore, the M156 served as a bridge between the previous generation of supercharged V8s and the upcoming generation of turbocharged V6s and V8s.
This manual will teach you everything you need to know about the M156, including its history, characteristics, performance, dependability, and typical issues. First, let’s look at the history that led to the creation of the magnificent M156.
The M156 Engine’s History
The M156 was designed by AMG in the early 2000s and debuted for the 2006 model year. It was the M113 engine’s replacement, another highly regarded Mercedes-Benz engine. The engine is a 6.2L V8 that is advertised as a 6.3L. This is to pay tribute to Mercedes’ first mass-production V8, the 6.3L M100 engine.
The M156 was named international engine of the year in both 2009 and 2010, demonstrating its superior performance capabilities. The M156, on the other hand, is far from flawless. It has some reliability issues, particularly with the valve train, and the big 6.2L powertrain consumes a lot of gasoline. It also lacks aftermarket assistance, as most simple bolt-ons only provide marginal power boosts.
Nonetheless, the M156 was a solid engine during its production run, powering some fantastic cars such as the W204 C63 AMG, W221 S63 AMG, and its M159 variant was found in the ultra popular SLS AMG from 2010 to 2015. The M156 was developed and constructed entirely at AMG’s Affalterbach factory in Germany. It was eventually superseded by the M157 and M177 engines, two smaller, bi-turbo V8s that produced greater power.
The 6.2L Mercedes M156 engine specifications are as follows:
The M156 engine was used in the following vehicles:
- Mercedes-Benz E63 AMG 2007-2011
- Mercedes-Benz ML63 AMG 2007-2011
- Mercedes-Benz CLS63 AMG 2007-2011
- Mercedes-Benz S63 AMG 2007-2010
- Mercedes-Benz CL63 AMG 2007-2010
- Mercedes-Benz R63 AMG 2007
- Mercedes-Benz CLK63 AMG 2007-2009
- Mercedes-Benz SL63 AMG 2008-2011
- Mercedes-Benz C63 AMG 2008-2015
The M159, a slightly modified greater power output version of the M156, came in the following models:
- Mercedes-Benz SLS AMG 2011-2015
- Mercedes-AMG GT3 2016+
- Mercedes-AMG GT3 Evo 2020+
- Design of the M156 Engine
The M156 is a water-cooled, 6.2L V8 with a compression ratio of 11.3:1 with a silicon-aluminum block. The silicon-aluminum alloy reduces weight while allowing the block to shed heat quickly. It has a closed deck design with dual-overhead camshafts that operate 32 intake (40mm) and exhaust (34mm) valves. The engine is naturally aspirated, with a 102.2mm cylinder bore and a 94.6mm piston stroke.
The M156 was notable for being the first Mercedes engine to have its cylinder walls plasma coated with Nanoslide. Nanoslide is a twin-wire arc spray method that melts iron and carbon onto the surface of the cylinder walls. This hardens the walls while significantly reducing friction, making them stronger and smoother, and giving a nearly mirror-like gloss. It is an AMG-exclusive technology that claims to minimize friction by up to 50%. This minimizes EGTs and wear while maintaining performance by lowering cylinder temperatures.
Variable valve timing (VVT) was also introduced to the engine, which was controlled by an electro-hydraulic cam adjuster. It had a forged steel alloy crankshaft and hefty connecting rods that could withstand a lot of power. Except for the 2010+ C63, which has forged pistons and a lighter racing inspired crank, the M156 also has cast hyper-eutectic pistons.
M156 vs M159
Mercedes-Benz released an M159 (E 63) variation of the M156 for the 2010 SLS AMG. Several design changes resulted in a significant increase in power for the M159. For enhanced performance, the valve train, intake, and headers were all overhauled. A dry-sump oiling system replaced the M156’s wet-sump system, lowering the SLS AMG’s center of gravity and allowing for better weight distribution and handling.
The M159 was even featured in the Mercedes-AMG GT3, a high-performance race car that debuted in 2014. The redline was raised, and around 30 horsepower were added over the production model. The M159 was still used in the 2020 GT3 Evo, demonstrating that it is still a viable engine a decade after its original production finished.
Engine Performance of the M156
The M156’s remarkable performance is by far its most memorable feature. When it first appeared in 2006, the engine produced 451hp/465tq, but by 2010, the S63 AMG, E63 AMG, SL63 AMG, CL63 AMG, and CLS63 AMG all produced 518hp/465tq. It has a strong power band that pulls strongly all the way to the redline.
The M156 is a real heir to AMG’s racing legacy. The V8’s fantastic sound, responsiveness, and relatively high redline are all praised by reviewers. The usual redline for most vehicles is 7,250 RPMs, but some have been improved to run as high as 7,750 RPMs – quite impressive for such a powerful V8.
Performance Enhancements for the MBZ M156
While the M156 has jaw-dropping performance out of the box, it lacks the same level of aftermarket support as many Mercedes-Benz models. The engine does not respond well to intakes because the stock intake already flows smoothly and supplies enough cold air. The only proven intakes cost over $2,000 and barely produce 10whp at best – hardly a reasonable investment.
The only upgrades to the M156 that are genuinely worthwhile are tuning, exhaust headers, and forced induction. Forced induction will certainly produce the most power, but supercharger kits are pricey and the modification is far from simple. Exhaust headers and tuning are the greatest options for those interested in street builds or more moderate power gains.
Tuning will normally produce 40-50whp and 20-30wtq on an otherwise stock engine, and can be purchased as part of tiered power packages or alone. If you’re considering local tuning, talk to your tuner about which alternative they prefer.
The M156 has two types of exhaust headers: short-tube and long-tube. Long-tube headers, which might be catless or with high flow cats, replace the cats in the OEM exhaust. Remember that catless exhausts are banned on the street, therefore non-competition builds should employ shorty headers or high flow catted choices. Long-tube headers will produce 25-40whp, whereas short-tube headers will provide 15-20whp.
Throttle bodies and catbacks are two other popular M156 upgrades. Throttle bodies contribute 10-13hp, and catbacks add no more than 5hp. When used in conjunction with tune and exhaust headers, throttle bodies will provide better gains. Catbacks are excellent for sculpting and refining the M156’s exhaust tone, as sound is entirely subjective.
Power Limits of the Mercedes M156
The M156 is an impressively powerful engine. The stock bottom end is easily capable of withstanding 750-800hp, which is much beyond the scope of any street-based design. The unique piston design and closed deck block stand up very well to abuse and power, therefore most bolt-on combinations will not come close to challenging the block or internals’ limits.
M156 Engine Common Issues
While the M156’s bottom end can handle a lot of power, its overall reliability isn’t the best for an AMG engine. There are difficulties with the head bolts and several valve train components from the factory. Even on entirely stock vehicles, problems can arise, and out of warranty, they can be quite costly to repair.
Common M156 engine issues:
- Bolts for the head
- Lobes of the Camshaft
- Plates for Camshaft Adjustment
The majority of the problems are related to the valve train, specifically the camshaft. The face lifted design was supposed to solve the difficulties, but only a portion of them were addressed, as we will see later. Exacerbating the issue, the M156 has four cams, which means that replacement expenses quickly add up. A lawsuit was even filed against the engine due to flaws in the valve train components.
M156 Legal Action
After the M156 had been on the market for five years, disgruntled AMG owners filed a class action lawsuit against Mercedes over valve train issues, notably the steel valve lifters and cast nodular camshafts. According to the lawsuit, these parts were substandard, resulting in increased premature wear and failure. The claims claimed that AMG was aware of the problems since 2007, but did nothing to correct them.
The complaint was eventually dismissed in 2012 due to a lack of standing, there was no settlement, and AMG admitted no wrongdoing. However, the 2011+ M156 (the only model to continue using the M156 after 2011 was the C63 AMG) received revised lifters, possibly indicating that AMG was aware of the defect. The facelift also addressed long-standing concerns with the head bolts.
1) Mercedes-Benz M156 Head Bolt Issues
Prior to the 2011 facelift, the most common issue with the M156 engine was head bolts. Essentially, the original head bolts were poorly built and thus readily corroded, causing the bolts to dissolve and leak coolant into the combustion chamber through the cylinder heads. The tips of the bolts would totally snap off in some situations.
Thick white smoke from the exhaust, low coolant levels, and milky tinted oil are all signs of worn or cracked head bolts. The white smoke and coolant loss are caused by coolant entering the engine and being burned off. The milky tint of the oil suggests that coolant is flowing into it.
The M156 has upgraded head bolts from the factory for 2011+ cars, resolving the issue for those engines. Anyone experiencing M156 head bolt failure should replace them with the revised OEM head bolts. Of course, if you intend to push excessive power levels, head studs should be considered as well.
2) M156 Lifter Problems
The steel valve lifters are the most problematic aspect of the M156 valve train. These were the subject of the 2011 lawsuit, and it’s easy to see why. Lifters are used to close and open the intake and exhaust valves on the cylinders and are controlled by the camshaft lobes. However, the M156 lifters have been known to completely seize up in some cases due to oiling issues. Because the cam lobes are only hitting one area, they will wear out prematurely.
As a result, seized lifters can cause misfiring and spark difficulties, leading in CELs and limp mode. Mercedes eventually changed the design of the lifters to allow for better oiling, so eliminating the problem of premature wear and seizing. However, these have received mixed reviews, with some claiming that they did not help at all.
The lifters problem can be solved by either getting the upgraded part from AMG or, if you don’t trust it to work, using the lifters from the M159, the M156’s relative. Furthermore, the M159’s black series lifters have a special coating that reduces friction and wear. They are also far lighter than standard, allowing for improved performance. Many folks will swap out their OEM lifters with M159 lifters when they replace their head bolts, so keep that in mind if you have head bolt troubles.
3) MBZ 6.2L V8 Camshaft Lobes Worn
Worn cam lobes are another valve train issue on the M156, and they are linked to the lifter problem. The cam lobes, like the lifters, have oiling design flaws that affect lubrication. This was exacerbated by issues with the lifters, which, if seized, would wear the top of the cam lobes. This could result in severe scoring and, in some circumstances, compromise of the cam lobes.
Increased ticking noises from the valve train, especially on cold starts, are symptoms of worn camshaft lobes. Furthermore, if the problem becomes severe enough, it may cause misfires and spark issues in addition to the lifters.
There are two options for replacing worn cam lobes. The quickest, simplest, and least expensive remedy is to apply a lubricant additive, such as Ceratec or MOS2. However, this solution is more of a band-aid than anything else, and it does not address the root of the problem. The only method to completely eradicate the problem is to purchase aftermarket camshafts that are stronger and better built than OEM. Even for those wishing to add forced induction to their M156, there are various choices on the market.
Related : The FA24 Engine Manual
4) Camshaft Adjuster Plates That Are Worn
The camshaft adjuster plates are the M156 valve train’s last stage. Cam adjusters are in charge of adjusting an engine’s variable valve timing (VVT), which is critical for things like gas mileage and performance. The cam adjusters of the M156, on the other hand, were frequently faulty. The plates would become out of tolerance, causing oiling troubles and a lot of premature wear.
A loud rattling sound at startup, unexpected decreases in fuel economy, poor throttle response, and misfire and VVT codes are all symptoms of worn cam adjustment plates. Mercedes-AMG did, in fact, publish a factory service bulletin about the cam adjuster plates. It covered every model year and model that used the M156, including post-facelift C63 AMGs, which drivers continue to say have these difficulties.
The solution for worn plates is to replace them with OEM or aftermarket replacements. Replacing with OEM will almost always result in the same problem again after a while. In terms of aftermarket plates for the M156, 63Motorsports offers numerous options that are tougher and more lasting than standard.
M156 Engine Overview
Overall, the M156 is a highly powerful engine with a well-engineered bottom end. To go with the 500+hp engine that screams down the streets, it provides a throaty V8 tone that sounds thunderous and raspy. It’s been seen in some of the best-reviewed Mercedes of the recent decade, including the W204 C63 AMG and SLS AMG.
However, the engine is not without flaws. Head bolts on pre-2011 vehicles were poorly designed and constructed, prone to leaking and breaking. The valve train had a number of troubles as well, particularly with the lifters, cam lobes, and cam adjuster plates. Mercedes admitted several of these faults, but their solutions (with the exception of the head bolts) were inadequate.
Nonetheless, the M156 is a standout engine that drivers laud for its performance and ability to handle high power levels. The fact that Mercedes-AMG is still using it in the next edition of their GT3 Evo in 2020 demonstrates how respectable and well-designed it is. While it does not respond well to most bolt-ons, exhaust headers and tuning can produce significant gains.