The Mercedes M272 is an engine series with a lot to offer, yet with its own set of faults. Between 2004 and 2011, the M272 series, including E25, E30, and E35 V6 variants powered a massive portion of the Mercedes fleet, ranging from cars as small as the SLK 350 to cars as large as the GLK 350. People generally regard these engines as strong, smooth, and capable.
However, they are also known for a handful of issues, with balance shaft failure being not only the most prevalent but the most serious. Over time, the balance shafts of certain M272 engines that fell in a window of production would wear at an accelerated rate, eventually causing them to fail and interrupt timing to at least one bank of the engine, requiring a rebuild, as the M272 is an interference engine.
In this guide, we’ll take an in-depth look at the infamous Mercedes M272 balance shaft issue, discussing which vehicles were affected, how to find if your vehicle is at risk, the common symptoms and codes, and what to do about it if your Mercedes is affected.
What is Balance Shaft 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. That is seriously no bueno on an interference engine like the M272. 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 (which we’ll cover shortly) often arise far before complete failure occurs. It is also important to note that Mercedes eventually remedied the issue on late model M272 engines (after 2007), but it is still a good idea to use a VIN decoder to determine if your vehicle has the improved shaft. We’ll give instructions on how to do that in a later section.
Balance Shaft Failure Symptoms
- Excessive engine rattle/vibrations
- Uneven idle
- 1200 (Mercedes) / P0016 (Generic) engine codes
- 1208 (Mercedes) /P0017 (Generic) engine codes
As I said, it is very rare that the balance shaft will fail immediately and without notice. In fact, you’ll likely experience tell-tale symptoms far before the shaft fails completely. A check engine light accompanied by numerous engine codes will typically precede the balance shaft failing by quite a bit. Like a few thousand miles in most cases. The most common codes are P0016 and P0017, which are the generic OBDII codes, or 1200 and 1208 if you are using a Mercedes-specific reader.
Those codes pertain to the intake camshaft sensor on right cylinder bank (P0016) and the exhaust camshaft sensor on right cylinder bank (P0017).If your vehicle displays those codes simultaneously, it’s fair to assume that a faulty balance shaft is causing them. While it’s possible that something else causes one or both of the codes, in a vast number of cases, the balance shaft is to blame.
Outside of engine codes, it will be pretty clear that there is something questionable going on, just by the way that the engine is acting. If the balance shaft gear teeth aren’t making sufficient contact with the chain, the shaft won’t spin at all. That will cause a significant increase in engine vibration to the point that you’ll definitely notice. Outside of those symptoms, misfires and rough idle are also possible but less common.
According to most reports, the balance shaft issue affected early model M272s (2005-2007) the most, as they used weaker metal for the balance shaft sprocket. We’ll get into more detail about how to determine if your exact vehicle was affected by the balance shaft issue in the next section. It is also important to note that while early model engines were impacted the most, even late model engines with the revised sprocket still can experience the same issue. The following models have the highest failure rate:
- 2004–2008 SLK350
- 2004–2008 CLS350
- 2005–2008 CLK350
- 2005–2008 C350
- 2005–2008 E350
- 2005–2008 S350
- 2005–2008 SL350
- 2006–2008 R350
- 2006–2008 ML350
- 2006–2008 Sprinter
- 2004–2008 SLK280
- 2005–2008 CLS280
- 2005–2008 CLK280
- 2005–2008 C280
- 2005–2008 E280
- 2005–2008 SL280
- 2006–2008 R280
- 2007–2008 S280
How to Determine If Your Mercedes Is At Risk
Outside of looking at the list above and guestimating if your vehicle falls into the at-risk category, there is a more fail-proof approach. It is actually possible to find out if your individual car has the faulty balance shaft installed by checking your VIN and your corresponding engine serial number by using a VIN decoder.
Okay, there is potential for this to get relatively confusing, so stick with me. Mercedes eventually recognized the balance shaft issue as a problem and installed revised the gear on late-model engines. That changeover occurred at a specific point in the engine production run. As a result, all engines with Serial No. 2729…30 468993 or later aren’t affected as frequently by the issue. The last eight digits of the engine serial number are what you are looking for, as all of the digits prior to that are the same. So, for instance, engine serial number 30 376901 would be affected and 30 539056 would not be.
So, how do you find your engine’s serial number? There are a number of VIN decoder websites available that allow you to enter your VIN and see the part numbers of every component on the car. The site hyperlinked here is a good one that doesn’t cost any money and is straightforward to use. Simply enter your VIN and scroll down to the section labeled “Engine No.” and the engine serial number is listed there. Once again, only the last 8 digits, beginning with ‘30’ matter here. Lower than Serial No. 2729…30 468993 and your vehicle is at risk. Higher than Serial No. 2729…30 468993 and you should be good.
Mercedes Balance Shaft Failure Fixes
Unfortunately, this isn’t a good problem to have, simply because the balance shaft is in an extremely inconvenient location to access, essentially requiring a full engine-out repair. For that reason, it is also an expensive problem to have. Whether you opt to have the repair done at an independent shop or a certified Mercedes dealer, you’ll be looking at a repair bill somewhere in the ballpark of $4,500-$6,000. That’s a pretty hefty bill, especially for a car that is over 15 years old.
For that reason, many M272 owners who experience this problem cut their losses. In some cases, it might be more financially feasible to trade or upgrade instead of fixing the issue. However, there are a couple of options available if you don’t want to get rid of the vehicle.
One option is to shop around to find a certified and reputable shop that will perform the replacement for the least amount. Obviously, it is a good idea to read shop reviews and customer reports before you have the repair done.
The other option is to attempt the repair yourself. Since it is such an involved job, I wouldn’t recommend trying the repair unless you have some pretty in-depth knowledge about technical engine operation. It is an engine-out repair that requires some specialty tools. The parts themselves also cost in the ballpark of $1,000. If you don’t feel qualified to do the repair, it is probably best left to professionals. If you want to see what the repair entails, I’ll link a video that covers the repair process below.
Mercedes Balance Shaft Failure Is As Unfortunate As It Is Common
While Mercedes hasn’t released an exact figure, it is estimated that approximately 20-25% of M272-equipped vehicles have experienced, or will experience, balance shaft failure during the vehicles lifespan. That is a ridiculously high figure for a problem that can be so catastrophic in the long term. In fact, it was such a widespread problem that Mercedes owners started a class action lawsuit about the issue. Unfortunately, the class action suit only covered vehicles 10 years or 125,000 miles past their manufactured date, so no vehicles are still eligible for compensation at this point.
At this point in time, if you experience balance shaft failure on your M272-powered Mercedes, it might be best to move on, unfortunately. Since the repair generally adds up to around the cost of the vehicle itself, it might not be worth throwing money at the problem, unless you are a capable mechanic.
If you are interested in learning more about the Mercedes M272 and its issues, take a look at our more complete Mercedes M272 Common Problems Guide.