The Mercedes M272 represented a massive step forward for Mercedes engine technology, as the M112 and M113 engines that preceded the new V6 engine family were quite old and outdated by the time that the turn of the century rolled around. The earlier engines were single-cam, three-valve-per-cylinder experiments in a way, as the M112 and M113 were the first V6 engines that Mercedes developed. The M272 implemented everything that Mercedes learned from the earlier engines and brought those lessons to a more modern package.
In this guide, we’ll cover the Mercedes M272 in detail, going over the engine’s specs, overall design, variants, common problems, and popular modifications.
Like Mercedes’ previous V6 entities, the M272 is a 90-degree V6 engine. Over the course of the M272’s service life, it existed in three different displacements, including 2.5L, 3.0L, and 3.5L variants.
|2.5 liters (2,496 cc), 3.0L (2,996 cc), 3.5L (3,498 cc)
|90 Degree V6
|Bore and Stroke
|88 mm × 68.4 mm (E25) 88 mm × 82 mm (E30) 92.9 mm × 86 mm (E35)
|DOHC- 24-valve- 4-valves per cylinder
|Variable Valve Timing
|Port Injection, Direct Injection on E35 CGI Variant
Two areas that Mercedes really focused on while developing the M272 were lightness and strength. The M272 features all-aluminum construction including both the block and cylinder head. Like many other manufacturers were doing at the time, the M272’s cylinder liners are made from a combination of silicone and aluminum, often referred to as alusil.
The M272’s rotating assembly was also beefed up. Some of the highlights include forged steel connecting rods, an ultra-light one-piece crankshaft, iron-coated aluminum pistons, and a two-stage variable-length intake manifold. The intake manifold itself contained swirl flaps to improve low-rpm performance.
M112 vs M272
While the M272 is technically based on the earlier M112 and M113 engines, in many ways it was a blank sheet design. While the simplistic V6 design of the M112 and M113 made them unrelentingly reliable, they lacked in almost every way compared to the M272. The M272 is undoubtedly more sophisticated, efficient, and performance-oriented. A lot of that had to do with all of the modern tech that Mercedes crammed into the engine.
The block itself is a reworked version of the one found on the earlier engines, but used Silitec cylinder liners. That significantly increased cylinder rigidity. While there are some differences between the blocks, the real difference between the engines is in the cylinder head design. The M272 added two additional camshafts and one additional valve per cylinder, making it a DOHC 4-valve-per-cylinder engine. Continuously variable valve timing was also added to the engine on both the intake and exhaust cams, improving fuel economy and high-rpm performance. The M272 dropped the M112’s dual spark plug per cylinder system in favor of a traditional single spark plug setup.
The final notable difference between the engines is the M272’s use of an electronically assisted thermostat. The M112’s thermostat is completely mechanical, meaning that it is operated entirely by coolant temperature. The 272’s electronic coolant flow control system improves engine warmup and is more responsive overall.
The Mercedes M272 has a firing order of 143625, with cylinder number one being the closest cylinder to the front of the car on the passenger’s side. You can reference the picture below if you are trying to locate a particular cylinder for a spark plug or coil pack replacement.
Since its release in 2004, a wide array of different vehicles has featured three different variants of the M272. Those include the M272 E25, E30, and E35. The only difference between the variants of the engine is displacement. They are pretty self-explanatory too, with the number corresponding with the displacement. For example, the E25 is a 2.5L engine, the E30 is a 3.0L engine, and the E35 is a 3.5L engine. Here’s how that breaks down into the bore and stroke of each variant:
E25 – 88 mm × 68.4 mm (3.46 in × 2.69 in)
E30 – 88 mm × 82 mm (3.46 in × 3.23 in)
E35 – 92.9 mm × 86 mm (3.66 in × 3.39 in)
It is pretty easy to tell which engines were used in which cars, too. The E25 was used in 2005-2011 models with badges ending in 230 (i.e. C 230 or E 230). The E30 was used in models with badges ending in either 280 or 300 (i.e. SLK 280 or C 300). Finally, the E35 was used in models with badges ending in 350 (i.e. C 350 or ML 350).
There is one more M272 to mention, and that is the E35 CGI variant. As opposed to all of the other variants, the CGI, which was released in 2006, was the only one to receive a direct injection fuel system. The direct-injected variant bumped power up to 288 horsepower and got better fuel economy than the port-injected E35.
Reliability and Common Problems
- Balance Shaft Gear
- Intake Manifold Issues
- Camshaft Position Sensor Failure
The M272 has overwhelmingly positive reviews when it comes to reliability. However, the few problems that the engine does have can be pretty serious and costly to repair. Early engines, in particular, can experience potentially catastrophic issues with their balance shafts, which may necessitate an engine out repair. The other known M272 problems aren’t quite as serious as that one, but can still be costly and time-consuming to fix. Let’s break them down.
Balance Shaft Gear Failure
As with almost every production V6 engine, the Mercedes M272 requires balance shafts to reduce engine vibration caused by the V6 engine’s inherently unbalanced design. They make V6 engines usable in luxury cars, otherwise, it would feel like driving a tractor down the highway at all times. They also connect to some critical components of the engine, including the timing chain. The chain rides on the teeth of the balance shaft gear, which spins the shaft within the bottom end of the engine.
Over time, wear or grinding down occurs on the teeth of the balance shaft gear, causing the timing chain to either slip off completely or skip timing. A skipped timing event like that can allow the pistons to make contact with the valves, bending them and potentially causing damage to the pistons and other internal components. That means either a rebuild of the affected cylinder head or, if you were seriously unlucky, a complete engine rebuild.
The good news is that balance shaft failure is a gradual process that typically worsens over thousands of miles. It is very unlikely that the shaft gear fails without you having a clue that it’s on its way out. Engine code and other symptoms often arise far before complete failure occurs. It is also important to note that Mercedes eventually remedied the issue on late model M272 engines.
I won’t go much further into the issue here, as I have already written a full article on M272 balance shaft failure that you can read here if you are looking for more information on the problem.
Intake Manifold Issues
Outside of the balance shaft gear issue, the M272 also suffers from intake manifold issues. In fact, it is widely known in the Merc community that the factory intake manifold design isn’t great, with most M272 owners dealing with the issue over the course of their vehicle’s life.
The problem originates from the design of the M272’s variable-length runner intake manifold. Inside the manifold itself, there is a flap that effectively splits the runners into low-rpm and high-rpm runner lengths that perform better in their respective rev ranges. The first set of runners provides better performance at low engine speeds, then the flap switches over to the second set of runners once a certain rpm is reached which provides better performance at high engine speeds.
The M272 returns oil vapor and other crankcase gases back into the intake manifold through its PCV system, where they are burned off in the combustion chamber. Over time, the oil and other residue can clog the flap, causing the actuators and plastic linkage to break. That prevents the flap from switching between the runners, causing a major decline in performance and typically a P2004 engine code. The problem usually occurs around the 80,000-100,000 mile mark. However, it can happen earlier, as I actually experienced the problem at around 60,000 miles on my mother’s C300.
While there are repair kits available to fix the issue, the best course of action is to replace the faulty manifold with the newer, redesigned manifold. I ended up replacing my mom’s faulty manifold with an aftermarket Pierburg manifold and the problem hasn’t returned 30,000 miles later.
Camshaft Position Sensor Failure
The M272 is also known to have issues with its camshaft position sensors. The engine has four dedicated sensors for each camshaft and all of them are equally likely to fail or present issues. It is important to fix the issue as CPSs play a pretty important role in engine function. Basically, they are magnetic devices with a solenoid that gather information about each camshaft’s speed and report it back to the ECU. The ECU uses that info to calculate engine timing and fuel injection.
A failing camshaft position sensor always triggers a check engine light, with the most common ones being P0011, P0012, and P0014. Other common symptoms include frequent stalling, rough idle, random rpm drops, poor gas mileage, a significant loss in performance, and weak engine responsiveness. If you don’t replace the cam position sensor quickly, your car might not even start.
The good news is that replacing a cam position sensor on the M272 is pretty inexpensive and straightforward. You don’t have to remove any auxiliary engine components if the faulty sensor is on the passenger bank. The sensors on the driver’s side are a bit harder to access, as you have to remove the power steering pump. With that being said, the sensors themselves are only around $25 and it only takes around 25-30 minutes of work if you are handy with a wrench. I’ll link a video below that shows the process of replacing the sensor.
- Upgraded Camshafts
It’s no secret that the M272 is not a very modifiable engine. A lot of that boils down to the fact that it is a relatively complicated naturally aspirated engine which is never a very good recipe for modifiability. However, there are a few worthwhile modifications that you can do to an M272 engine that will yield some moderate power gains. It’s just important to remember that you won’t be gaining heaps of power like you would on a turbocharged engine.
- 15-30+whp gains
- High-rpm powerband
In most cases, and especially with naturally aspirated V8s, camshaft upgrades are the key to making a ridiculous amount of power. It’s a bit more complicated with the M272. The long and short of it is that it’s unrealistic to expect massive performance gains from upgraded cams, which makes it hard to justify the cost and difficulty of installing them. On the forums, enthusiasts have said that they gained around 15-20 horsepower and a similar amount of torque from the Schrick M272 cams, which also happen to be the only aftermarket off-the-shelf cam option for the engine.
For north of $2,500, the power and torque gains alone aren’t worth the price. Installing cams is really only worth it if you’re planning on taking your Merc to track days. The Schrick cams move the power curve higher in the rev range, meaning that the engine will produce the most power at high rpms. That is beneficial on track, where you spend most of the time high in the rev range. However, that is at the sacrifice of low rpm performance and torque.
While a camshaft upgrade is worth it for M272 owners who are planning on spending most of their time at the track, it is not a good upgrade for daily drivers or street applications for that matter.
- Louder, aggressive exhaust sounds
Headers offer some of the best power gains for the Mercedes M272. If you’re looking for a noticeable boost in performance, headers should definitely be towards the top of the mod list. The main goal with headers is to improve exhaust gas flow and reduce back pressure. Since the exhaust manifold bolts directly to the engine, it offers the biggest gains of any part of the exhaust system. It’s best to combine headers with a quality tune to maximize their performance.
In addition to the impressive power and torque gains, it really wakes up the engine from a sound perspective, which is half of the fun anyway, right? Despite being a pretty worthwhile modification, there are only a few header options available for the M272. A couple of years back, Kleeman was the go-to brand for Merc headers, but since then, they stopped carrying M272 headers. If you can find a used set, those are definitely the ones to go with. One member on the MBWorld forum reported 30 horsepower gains on the dyno.
MBH Motorsports also carries a quality set of long tube headers for the M272. Unlike the Kleemans, the MBH headers are catless, meaning that they are meant for motorsport applications only, but enthusiasts have reported even more impressive gains from those.
- Similar torque gains
- Bigger gains from additional mods
- Better throttle response
- Improved MPG
While tunes generally provide more notable performance gains on engines that use forced induction, they can still up the performance on the M272 too. It’s not just about the power gains from the tune alone. Tuning is also the foundation for maximizing power gains from additional mods. As you begin adding more air and fuel it’s important to properly tune the computer (PCM) to account for the changes.
On a bone stock 272, you may only see power gains around 10-20whp with tuning. There is only so much power a tuner can squeeze out of a NA engine. Torque gains should fall in the same ballpark and you’ll likely notice better throttle and engine response. Depending on the specific tune you may also see better fuel economy. However, if you’re using the newfound power then that likely won’t be the case.
You will need a tuner device to flash the PCM. A tuner will run in the ballpark of $400-600 and often include some basic off-the-shelf tunes. Ultimately, a tune is a great upgrade as it’s relatively inexpensive for power gains while also helping to improve performance from other upgrades.
The Mercedes M272 Is a Bright Spot in the Mercedes V6 Catalog
After filling the shoes of the popular Mercedes M112 engine, the M272 proved its worth as a more modern and well-equipped V6 engine in the Mercedes lineup. The M272’s lightweight and strong construction makes it an effective powerhouse in any application ranging from the small 2-door SLK to the family-hauling GLK. New engine tech, like DOHC, 4-valves-per-cylinder, and variable valve timing, brought the M272 firmly into the 21st century.
The M272 has a pretty good reputation for reliability overall. However, it does have a couple of significant issues that knock it down a few pegs in terms of reliability. Early engines suffered from the balance shaft issue, which Mercedes later fixed. Intake manifold problems and camshaft position sensor failure also proved to be somewhat common.
The M272 truly isn’t a very modifiable engine. Some enthusiasts swap in performance cams for a better high-rpm powerband. Headers might be the most effective street-friendly modification since they improve power and torque without any drivability consequences. A tune can also tie all of those modifications together while also boosting power on its own.