Mercedes M159: Everything You Need To Know

The Mercedes M156 was introduced in the E-class model in 2006 with the E 63 model designation. This engine replaced the much revered supercharged M113 V8, bringing the flags of naturally-aspirated to be raised again.

Throughout the years, it became successful as well as the development of the engines in that family. The confidence and faith of Mercedes AMG in M156 prompted them to release a high-performance version, more powerful than the M156, to carry on the capabilities and legacy of the M156 engine. Hence the birth of the Mercedes AMG M159 engine.

Let’s dive in and talk about M159’s development, design, reliability, and many more.

What are Mercedes M159 Engines?

The Mercedes M159 engine is a further development of the eight-cylinder 6.2 Liter M156 engine. This is the version used to power the Mercedes-Benz SLS AMG and the current AMG GT3 race cars. The M159 engine was extensively revised, especially the intake manifold and the pistons; furthermore, Mercedes AMG installed dry-sump lubrication for a lower center of gravity resulting in oil sufficiency in cornering and speed.

Compared to the usual AMG engine, the M159 or SLS includes:

  • A reworked valve train and camshafts.
  • Intake system.
  • Better exhaust system.
  • The use of flow-optimized tubular steel headers.

The M159 engine version has a higher output than the M156 since its primary objective is to power high-performance vehicles.

Engine Specifications and Design:

  • Production Run: 2006 – Present
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: V8
  • Bore: 102.2 mm
  • Stroke: 94.6 mm
  • Valvetrain: DOHC four valves per cylinder
  • Displacement: 6.2 L (6208 cc) marketed as 6.3 L
  • Compression Ratio: 11.3
  • Weight: 452 lbs.
  • Maximum HP: 622 HP at 6,800 RPM
  • Maximum Torque: 479 lb-ft at 5,000 RPM

The Mercedes M159 engine is a naturally-aspirated, water-cooled, eight-cylinder gasoline engine. It has a 6.2 Liter capacity but is marketed as a 6.3 Liter. The cylinder bore diameter is 102.2 mm, a piston stroke of 94.6 mm, and an 11.3 compression rating. As we mentioned earlier, this engine is the developed version of the M156.

It has the same cylinder bank design with M156, arranged in a ‘V’ configuration that features a robust aluminum head with four valves per cylinder and dual overhead camshafts. The bucket-type followers actuate the series of 32 valves, resulting in a tight and compact valvetrain capable of much higher power output.

The cylinder block is made from lightweight aluminum material. It features a closed-deck design inspired by high-performance racing engines, the same concept they used on the SLR McLaren’s M155.

AMG M159 followed the footsteps of the M156 engine, which was the first mass-produced engine to use a wire-arc spray coating called Nanoslide on the cylinder walls. Mercedes equipped this technology on M159 to increase its durability and reduce the friction by almost half, around 230-degrees Fahrenheit compared to traditional cast-iron cylinder liners.

The crankshaft of M159 is made from a forged steel alloy, and the connecting rods are also based on the concept found in modern racing engines. The standard M159 versions came with a whole lot of new forged pistons and camshafts.

Different from the naturally aspirated AMG M113 and the supercharged powerhouse M113K, M159 engines, like the M156, use only one spark plug per cylinder – contrary to the two. Furthermore, Mercedes also included a variable valve timing system for both the intake and exhaust valves, operated through an electro-hydraulic cam adjuster.

The Mercedes AMG M159 appears in Mercedes-Benz SLS AMG and AMG GT3.

Engine Tuning, Modifications, and Upgrades:

There’s nothing much you can do on the already-refined piece of craftsmanship right here. The engine development of the M156 family is outstanding and should be given the proper recognition. You know, even without the tuning and upgrades, M159 is brute, monstrous, and a high-performance beast.

With the peak power hitting 600s, there should be no debates regarding this engine’s capabilities and reliability. Those internals are bound to get things done on the power and torque end. I surmise that in even 700s or low 800s, the M159 can still withstand those.

However, if you decided to go more aggressive, you will need either replacement of headers or forced induction – two choices at your disposal.

Some steps or stages need to be done to fine-tune your M159 engine. The first stage is most likely the ECU reflashing, a performance exhaust manifold, and replacing the camshaft profile.

You will purchase a fuel pump upgrade, high-flow fuel injectors, and catalyst in the next stage. Add that with the forced-induction kit, ported and polished head, change the internals, and install larger valves. With these upgrades, you can hit the 660-670 HP.

The last stage upgrade is tedious and quite expensive, but it is worth it since it can tap the elusive but reachable 1000 HP line. You will need a 3.0 L twin-screw compressor module, 1000 HP liquid to air intercooler, high flow fuel rail system, high capacity fuel injectors, and molded silicone couplers.

Throw in some aftermarket parts such as an intercooler water recovery tank, 8-rib Direct drive belt system, and cross-flow heat exchanger. Buy an intercooler water pump, power-steering reservoir relocation assembly, and Weistec Engineering Stage 3 Supercharger System ECU reflash.

Problems Surrounding Mercedes AMG M159 Engines:

As a product of an automaker with a long history of great engines, the M159 is no exception to the terrors of deterioration, age, mileage, and wear. These are all typical happenings for the engine as the stress induced on the moving parts starts to take a toll on them. Here are some troubles you might encounter with the M159 machine.

The first issue is the crankcase breather valve. There are two ways in how the breather valve fails. The most common is the deterioration of the diaphragm valve; the other way is the hose from the crankcase going to the valves starts to become brittle and develops cracks. This issue worsens over time and may lead to increased oil burning, misfires, and excessive smoke from the tailpipe.

This leads us to the next issue that took serious casualties and affected large numbers of engines. Oil leaks affected M159 when its camshaft solenoid cover gaskets, valve cover gaskets, and oil filter housing gaskets start to fail. These are standard maintenance items, so they should be replaced periodically.

If oil leaks remain unattended, this can damage peripheral components like the drive belt pulleys, alternator, air conditioning compressor, drive belt, and transmission cooling hoses.

There is also an issue concerning noise at cold start and continues at any engine RPM, can be cold or operating temperatures. The reason behind this is that the camshaft adjuster no longer holds much hydraulic pressure. This is observed mainly on engine startup.

The plastic-made drive belt pulley design of the AMG 159 engine has a pressed-on bearing which triggers a faulty drive pulley. Pulley failure in the engine can damage the drive belt, and when that happens, the belt can also damage the coolant breather port on the thermostat.

Mercedes-Benz AMG M159 was also affected by the cylinder head bolts that tend to break, allowing the coolant to infiltrate the combustion chamber. That is why it is recommended to update the older design bolts with new ones.

The magnesium intake manifold also has some troubles since it houses the engine’s twin throttle bodies. The center mounting plate starts to deteriorate over time, causing rough idling in some situations.

Other M159 issues that need to be addressed are the camshaft and Hydraulic Lifters. You should consider these components regular maintenance items because they wear around 90,000 – 100,000 miles. The wear happens on the left and right intake camshafts, and if not resolved, the cam lobe will eat through the hydraulic lifter.

Also, engines with high mileage should have the oil checked or valve covers for any signs of wear.

Summary

The Mercedes AMG M159 does not have a significant difference from its close sibling M156 engine. Mercedes highlighted M156 weaknesses and fitted the newer M159 to higher performance vehicles to designate M156 as a mainstay engine for 63s; while the M159s for the SLS.

Not a direct competition with each other, but M159 has higher power and torque, making it a better suit for its application. If you switch them, both engines would still be good but not as effective as they are.

The reworked M159 defined itself and will likely stay in the long run.

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