The Mercedes-Benz M272 engine is the notoriously smooth, competent V6 power plant used across various models and trims from 2005 onwards. Be it the 2.5L, 3.0L, or 3.5L variants (E25, E30, and E35, respectively), all M272 engines share a common failure point: their variable intake manifold swirl flaps. Although a great design, parts wear, and the manifold suffers. Luckily, there’s a little-known fix that improves performance and eliminates future failures.
Mercedes-Benz M272 V6 Intake Manifold Design
The factory M272 magnesium intake manifold sold across nearly all M272 cars has a bit of clever engineering hidden within. At a time when emissions restrictions were tightening, and cars were getting larger, Mercedes turned to a bit of science and the evolution of a design Daimler Benz patented in 1958.
Although it sounds unbelievable, the length of the tube leading into the intake valve has a definitive effect on power output and delivery. Because of that phenomenon, non-variable manifolds are only most efficient in a small section of the rev range, leaving better performance and fuel economy on the table. Variable intake manifolds work around that by using “Swirl flaps,” variable-position air deflectors within the manifold that move with throttle input to control the volume and force of the air directed into the engine for maximum efficiency. As they move, they change flow characteristics, providing a better combustion.
Although widespread across the Mercedes lineup, these flaps are all prone to failure as they age. For cost and weight reasons, Mercedes used plastic for the actuator arm assembly, and the repeated thermal stress over the years makes them brittle, while oil gunk from a common PCV failure reduces range of motion. Symptoms include decreased performance and acceleration, hindered fuel economy, and a check engine light. Most commonly, the plastic arm at the front of the intake manifold (which physically moves the flaps) breaks with age as oil accumulates atop the flaps, hindering motion and keeping flaps either stuck open or closed.
Codes Associated with Intake Flap Failure:
- P2004 (tumble flaps stuck in actuated position)
- P2005 (mechanical fault of one actuating lever)
- P2006 (stuck in non-actuated position)
A common M272 or M273 misnomer is that the most straightforward fix is replacing the flap’s plastic actuator arm on the front of the manifold with a metal one. That’s typically effective in shutting off the check engine light but won’t prevent further failure. The internal bushings that hold the unit inside the manifold can also wear, causing a flap to fall into the engine’s top end. To ward this off, the most common recommendation is a complete manifold replacement to ensure the engine’s safety.
Retrofitting The M272 V6 Composite Intake Manifold
Replacing the intake manifold with a new one isn’t as difficult as it may seem. It’s a lot of disconnecting old electrical connections and fiddling with vacuum lines, but the process is relatively straightforward. The only downside is potentially replacing the manifold with another one that will eventually break like the first. Luckily, there’s another way to remedy the issue on M272-equipped vehicles.
2009 was memorable for many reasons, but few would choose the emergence of an updated 3.5L M272 for the R171 SLK350 as a standout. Designated under the option code "M014" for increased performance, it punched out an extra 30 hp and 50 lb-ft thanks to a handful of tweaks like revised exhaust manifolds, cylinder heads, and camshafts, bringing the SLK much closer to its rival’s performance. However, another piece of that updated engine provides a solution.
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Atop the M014 engine sits an intake manifold free of flaps and metallic construction. It’s made of a black composite plastic material, and thanks to a simpler design, it eliminates the troublesome flaps entirely. Instead, it’s a more traditional manifold with a larger volume, meaning it’ll flow more air with less resistance. While not as advanced as the standard unit, its larger size allows it to breathe better everywhere, leading to a slight boost in power across the rev range, significantly more power at the top of the rev range, and even improved fuel economy while benefiting from increased reliability. Additionally, the manifold comes off of the shelf from Mercedes, sized for a throttle body with a diameter 8mm greater than the stock M272 unit, adding to the "plug-and-play upgrade" nature of the M014 manifold.
This is a relatively simple modification for anyone willing to invest in their M272 and is one of the only tried-and-true power adders. Gaining reliability is a relatively rare bonus with any performance modification, too. If you don’t mind a bit of extra work and are willing to follow along with the information we've prepared for you, there are only benefits to be had!
Logistics & Parts For The M014 Intake Swap
Although the manifold does bolt onto any M272 V6, a few parts need to go along with it to ensure factory fitment, and first up is a larger throttle body.
The 82mm throttle body used on M014 cars was a clever use of the Mercedes parts bin, as the same part used on the late M014 R171 roadsters is stolen from the same-generation M273 V8 engine. A throttle body swapped from a CLK550, E550, S550, and any other vehicle with the part number 2731410325 will work perfectly. It is; however, a mandatory upgrade as the opening on the front of the intake is too large for the 74mm unit sold on most M272 cars.
As the throttle body is larger, you must upsize to an M273-sourced air deflector boot, which connects the MAF to the throttle body. This is included in our M014 intake manifold swap kit and will also have brand-new seals. From here, an ECU tune is strongly recommended; this modification will remove a bit of mid-range torque by deleting the flaps at the expense of the top-end power upgrade provided by increased airflow. A tune can help counter the loss of mid-range torque a bit for around-town drivability and ensure that fuel delivery is safe for the increased air volume.
