Mercedes M273: Everything You Need To Know

The comfort and luxury of the Mercedes-Benz vehicles left an excellent impression on those who experienced it. But there is more than just that; Mercedes also took a serious note on high engine performance and reliability, incorporating it with their style.

Introduced by Mercedes-Benz in the 2005 SLK, the new-generation engine M273 gained a place in the automotive world in pioneering the four-valve per cylinder, dual overhead camshaft design in Mercedes-made machines.

It continues to shine throughout the years but festered with some unforeseeable instances. But the question stands still, what is the legacy left by the M273 engine, and how it affected the following engine releases of the German automaker.

What are Mercedes M273 Engines?

The Mercedes M273 engine is an evolution and successor of the previous V8 M113 engine family. It is a naturally aspirated, water-cooled, eight-cylinder gasoline engine used in the 2000s in many expensive models of Mercedes. M273 engines were based on the identical M272 V6 introduced in 2004.

The M273 family was released in 2005 and offered two displacement variations – the 4.7 Liter and a 5.5 liter V8s. Gone were the days of the three-valve single cam in M112 and M113 – replaced by a four-valve per cylinder, four-cam machine with independent continuously variable valve timing on both the intake and exhaust sides; Mercedes also added a balance shaft.

The changes it undergone produced a brand new engine that can produce more power with lesser emissions and noise compared to the outgoing M112 and M113 engines.

In 2010, Daimler AG launched the 4.6 Liter V8 twin-turbocharged Mercedes-Benz M278 engine as a replacement for the M273 engine.

Engine Specifications and Design:

  • Production Run: 2005 – 2019
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: V8
  • Bore: 92.9 mm (4.7 L) and 98.0 mm (5.5 L)
  • Stroke: 86.0 mm (4.7 L) and 90.5 mm (5.5 L)
  • Valvetrain: DOHC four valves per cylinder
  • Displacement: 4.7 L (4663 cc) and 5.5 L (5461 cc)
  • Compression Ratio: 10.7
  • Weight: 450 lbs.
  • Maximum HP: 382 HP at 6,000 RPM
  • Maximum Torque: 391 lb-ft at 2,800 – 4,800 RPM

As we mentioned above, there are two variants for the M273 engine – the 4.7 L and the 5.5 L. Still, they have the same characteristics as described below: aluminum blocks, forged steel connecting rods, sequential fuel injection, one-piece cast camshaft, and an aluminum-magnesium intake manifold and tumble flaps which provides a variable length of the intake channels.

All of the Mercedes M273 engines comprise an all-aluminum lineup – the cylinder block and heads. The M273 has a 90-degree cylinder bank angle arranged in a ‘V’ configuration with Aluminum-Silicon alloy (Silitec) cast cylinder liners.

The aluminum crankcase has reinforced bearing caps and five main bearings, which tightly secures the crankshaft inside through these caps. The M273 is equipped with a fracture-split 70MnVS4 forged connecting rods and low-friction, lightweight aluminum pistons.

Mercedes replaced the old style three valves and single cam with the integration of four valves per cylinder and double overhead one-piece camshafts for the M273 engine. The intake camshafts are driven by a duplex chain (double-strand timing chain), while the exhaust camshafts are gear-driven through a sprocket at the front of each intake camshaft.

The M273 features an independent intake and exhaust cam timing. It uses a sequential fuel injection managed by the Bosch ME9 ECU with two microcontrollers; the ECU also controls cooling. Mercedes installed a new electronically-controlled instead of the mechanical thermostat for the optimal regulation of engine temperature.

Mercedes M273 E47:

The E47 is the 4.7-liter version. It has a cylinder bore of 92.9 mm and a piston stroke of 86 mm. The rated output is 335 HP at 6,000 RPM with 339 lb-ft of torque at 2,700 – 5,000 RPM.

Applications: 

  • 2007 – 2012 GL 450
  • 2007 – 2013 S 450
  • 2007 – 2011 ML 450

Mercedes M273 E55:

The E55 is the 5.5 Liter version. It has an increased cylinder bore of 98 mm and a piston stroke of 90.5 mm. The rated output is 382 HP at 6,000 RPM with 391 lb-ft of torque at 2,800 – 4,000 RPM.

Applications:

  • 2006 – 2011 E 500 / E550
  • 2006 – 2010 CL 500 / CL 550
  • 2006 – 2010 CLD 500 / CLS 550
  • 2006 – 2012 GL 500 / GL 550
  • 2008 – 2011 ML 500 / ML 550
  • 2006 – 2009 S 500 / S 550
  • 2007 – 2012 SL 500 / SL 550
  • 2006 – 2009 CLK 500 / CLK 550
  • 2006 – 2015 G 500 / G550

Engine Tuning, Upgrades, and Modifications

The potential of the M273 engine to be upgraded or modded is excellent. Being a naturally aspirated engine has its pros and cons, but rest assured that N/A is amazing if you want to build a more personal one.

You can opt to have a supercharger installed, resulting in a massive boost of at least 475 HP without changing the internals. Kleeman and other companies offer a supercharger kit that also includes ECU tuning, of course.

Purchase aftermarket parts such as exhaust, headers, J or Y pipe rework, throttle body upgrade, fuel rail, TB unit, airbox upgrade, and tune the ECU. With that, you would also need the power to stop the power you gained. So, a big brake kit and new linings would suffice.

Problems Surrounding Mercedes M273 Engine:

Sad to say, but the M273 engine was plagued by numerous issues and earned the reputation as one of the most troublesome Mercedes V8 engines. However, these problems are unavoidable, and we can only do so much to try to resolve the issue.

Worn Guide Gear

In May 2011, Mercedes-Benz vehicles with M273 V8 engines, especially those manufactured prior to September 2006, were part of the service bulletin issued by Mercedes.

This announcement cites that some vehicles have worn guide gear for the timing chain. That wear can severely impair the positioning of the camshafts in the right cylinder bank.

According to the post, symptoms such as illumination of the check engine light; and diagnostic trouble codes (DTCs) 1208 or 1200 are stored in the ME-SFI control unit.

Since the September 2006 production, Mercedes used a more rigid material for the timing chain guide wheel to significantly reduce incidents and eliminate this issue entirely.

Oil leaks

Another issue of some M273 engines experience is oil leaks from the round plastic expansion plugs (cam plugs) on the rear side of the cylinder heads. This issue is more prevalent in those engines that were produced before June 2008.

One place you should always check for leaks is the electrical plugs for the cam adjuster magnets. These parts are notorious for leaking through the electrical connector, and the oil will make its way up the engine harness.

Another potential leak to look for is at the engine oil separator. It is described as a plastic cover sealed by a rubber O-ring; rings that will later become brittle and lose their effectiveness.

Spot for any oil residue on the retainer screws of the cover to specify if the cover is leaking.

Mercedes already addressed the issue by installing new cam plugs that are strong enough to prevent oil leaks.

Broken Actuator Cam

Suppose you notice rough idling, a loss of power, particularly at lower to mid-range engine speeds accompanied by the illumination of check engine lights. In that case, you might have a broken actuator cam.

The plastic actuator cam in the variable valve intake manifold is prone to carbon build-up due to oil venting from the positive crankcase ventilation (PCV) system. Carbon deposits accumulate on areas inside the intake manifold, such as the swirl flaps that used to vary the intake channel length.

These deposits make the flaps nasty, resulting in a higher plastic VIM load and increases the resistance on the plastic actuator cam. This causes the component to break, and other peripheral components can also fail – including the swirl flaps, vacuum diaphragm, and actuator mounting arms.

Engine Thermostat

This is the most common failure we encounter on the M273 engine – map-controlled thermostat.

The electronically-controlled thermostat is primarily made to regulate the coolant temperature efficiently between 185 F to 221 F. However, temperature fluctuations are expected with properly operating thermostats, but not that often.

Upper Guide Pulley 

The upper guide pulleys of the M273 experience a much stronger bearing wear than all other pulleys on the system. The two guide pulleys are mounted on the water pump for the serpentine belt type system.

A high-pitched noise during operations can be heard. When these pulleys fail, they will tear up the belt leading to the loss of all accessory drive components – power steering pump, water pump, and alternator.

Idler pulleys and belt tensioners should be replaced every 60,000 miles or imminently if you have no idea about the car’s maintenance history.

Summary

The Mercedes-Benz M273 engine is one of the closest things we have with the M272 V6. It is the product of life-long engine development, research, and expertise; especially, it reveres the great M113 family.

I am sharing the impression that this engine possesses the right balance of smooth operation, strong, reliable power, and impressive torque band.

It features a technologically advanced system at that time. New cooling system, new intake manifold, integration of dual-length Variable Length intake manifold, the switch from the three-valve system to four per cylinder, and a DOHC aluminum cylinder heads.

Mercedes M273 is widely used in the 2000s, but even with the strength in numbers, it was affected by some issues. Despite all the unpleasant presentation that M273 showed, it is still a great engine to have.

With a service life of more than 200,000 miles, M273 are the kind of engines you would not find sitting there in the garage. It is best suited to be high-performance and rolling!

I hope this answers some clouds in your head regarding the Mercedes-Benz M273 engine design, reliability, issues, overall impact on the automotive industry, and reliability.

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