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Mercedes ML350 2005-2011: Problems And Reliability Issues

Mercedes ML350 2005-2011: Problems And Reliability Issues

What kind of problems does a 2005 – 2011 Mercedes ML350 normally have? In this blog, we’ve outlined all the most important things you should watch for when you’re in the market for an ML350. However, let’s first start with a quick answer:

Most commonly, the 2005 – 2011 Mercedes ML350 has sound issues caused by failing engine parts. Furthermore, engine mounts can break, and window regulators can malfunction. Finally, the suspension is vulnerable to wear and tear, which can cause noises from the suspension and expensive repairs.

However, that doesn’t tell the whole story. In the rest of the article, we’ll discuss every single problem in detail. Furthermore, we’ll tell you how to identify it, fix it and how much it costs to fix. Read on!

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Also read: The Complete Cost Of Maintaining A Mercedes-Benz

1. Engine Running Louder Than Usual

Mercedes ML350 is notorious for the problems causing the engine to run louder than usual. In many 2005 – 2011 models, some common problems cause the engine to rattle and rumble.

If the engine in your Mercedes ML350 roars abnormally, it can be due to dirty spark plugs or a more serious issue like a failed catalytic converter or muffler. At the same time, some of the problems causing the engine to run louder are easy to fix. There are other problems as well, which are pretty expensive and time-consuming to fix.

Most problems that cause the engine of the Mercedes ML350 to run louder are related to the car’s exhaust system. Like other cars, the exhaust system in the ML350 is responsible for collecting and getting rid of the exhaust gases coming from the cylinder head. This whole process is accomplished with the help of the engine manifold, catalytic converter, muffler, and other small components.  

The catalytic converter in the ML350 removes harmful elements from the exhaust gases. At the same time, the muffler is responsible for reducing the noise levels before the gas exits from the tailpipe.

Any ML350 from 2005 – 2011 with a thunderous engine can have problems with the exhaust system and its components. Common reasons for the Mercedes ML350 to run louder include –

Failed Muffler

Mufflers in the Mercedes ML350 are constantly exposed to high heat and pressure. Besides, there are also subjected to grime, road salts, and weather. Over time a muffler can erode or develop holes and cracks, eventually leading to its failure.

Common symptoms of a failed muffler in the ML350 include – engine louder than usual, a significant drop in mileage, and increased exhaust fumes. Failure of the muffler usually occurs with older models. Fixing this problem would require immediate repairing or replacement of the muffler. If ignored, it can cause severe damage to the catalytic converter or the engine.  

The average cost of replacing the exhaust muffler in the ML350 is around $1100-$1200 in the United States.  

Clogged Catalytic Converter

The catalytic converter is a vital component of the ML350’s exhaust system. If failed, it can cause the engine to run roughly and loudly.

To detect any problem with the catalytic converter, look for these common symptoms –

  • Increased engine noise
  • The smell of rotten eggs from the exhaust
  • Illuminated ‘Check Engine’ light
  • Dark-colored exhaust smoke
  • Loss in acceleration
  • Extreme heat under the vehicle

If the catalytic converter worsens, it will not be able to burn the unburned hydrocarbons. Resulting in the rotten egg-like smell and the catalytic converter getting blocked. If this happens, the engine of your ML350 will not start or run properly. 

Replacing the catalytic converter of your Mercedes ML350 can cost you approximately $950 – $1,200 in the US.

Also, read Mercedes BlueTec Problems.

Damaged Or Broken Tail Pipe

Although it is rare for the tailpipe to get damaged, it can develop holes during harsh road conditions or if rusted. If this happens with the tailpipe of your ML350, then it would result in harsh engine noise. To fix this problem, you would need to repair the tailpipe.

Leakage In Exhaust Manifold

The exhaust manifold in your ML350 collects the waste gases from the engine. In case of any leak, it can cause the engine to run unevenly and loudly. In many cases, it also triggers the ‘Check Engine light.

This problem is serious because the leaking hot gases from the exhaust manifold can damage or melt the surrounding plastic components. Also, in case of severe leaks, the leaking exhaust gases can find their way into the cabin of your car.

Although this problem is prominent in older models of the ML350 and rarely occurs in the 2005-2011 models, if faced, it would require urgent repair of the exhaust manifold.

Worn Gaskets Or Seals

Another common culprit of the loud engine noise problem is the worn-out gaskets or seals. The exhaust system in the Mercedes ML350 2005 – 2011 models has quite a few gaskets and seals. If any of these fail, they can cause the engine to run louder than usual.

If your ML350 has high mileage, then there are chances of damage caused to the seals and gaskets over time. In this case, the damaged seal or gasket needs to be replaced. If not repaired, it can spoil the exhaust manifold, which will be more expensive to repair. The seal and gasket of the ML350 are inexpensive parts and can be replaced easily.

Malfunctioned Oxygen Sensor

The oxygen sensor in the ML350 measures the amount of oxygen in the exhaust gases when they leave the combustion chamber. Based on this data, ECU assesses the amount of fuel entering the engine.

Suppose the oxygen sensor in your Mercedes ML350 is dirty or goes bad. Then it can send incorrect data to the ECU, resulting in too little or too much oxygen going to the engine. Such a situation can cause the engine to run louder or rougher than usual.

The oxygen sensors in the ML350 are located either under the hood or under the car. It is screwed to the exhaust pipe, either in the back or front of the catalytic converter. A bad oxygen sensor can make the ‘Check Engine’ light illuminate. To accurately detect the problem with your oxygen sensor, you can take the help of an expert or an OBD scanner.

Fixing the problem with the oxygen sensor can cost a few hundred dollars in the United States.

Failed Or Dirty Spark Plugs

The spark plug is yet another crucial component that can cause the engine to misfire or make it run louder than normal. If the spark plug is dirty or faulty, it can cause improper ignition leading the engine of your ML350 to misfire and sputter. The problem with the spark plugs will ignite the ‘Check Engine light.

The total replacement cost of a spark plug can be around $450-$600 in the US. 

Faulty Mass Airflow Sensor

The mass airflow sensor in the ML350 measures the amount of air entering the FI (fuel injection) system. The data is fed into the ECU to determine the correct amount of fuel to the combustion chamber. A dirty mass airflow sensor in your ML350 can send the wrong amount of fuel to the engine, leading to a rough and loud engine running.

The faulty mass air flow sensor must be replaced with a new one, costing you a few hundred dollars in the US to fix this problem.

2. Problem With Engine Mounts

The 2005 – 2011 models of the Mercedes ML350 are infamous for the engine mount problem.

The engine mounts in the ML350 are made up of rubber and steel, serving two main purposes. One, it locks the engine to the frame of the car. Two, it absorbs shocks and engine vibrations so that passengers don’t feel the engine’s movement.

The Mercedes ML350 has multiple engine mounts. If any one of these mounts breaks, you will feel substantial engine vibration and movement on the steering, seat, and in the cabin. Also, since the mounts are oil-filled, therefore after 100,000 miles or so, they begin to fail and lose the oil.

If the engine of your ML350 feels more clunky, noisy, or vibrates irrationally. The possibilities are your engine mounts are damaged and need replacement.

Other common symptoms indicating the problem with the engine mounts include –

Bumpy Ride

Suppose any of your ML350’s engine mounts are faulty. You could end up with a bumpy ride since the engine mounts are responsible for absorbing vibrations from the engine and getting it into the cabin. Thus, if you experience a very bumpy ride, then chances are your engine mounts need attention.

Clunking And Rattling Noises

When the engine mounts fail, the car will begin to make some rattling and clunking noises. Moreover, if the mounts are not fixed, it will lead to rattling noises whenever you change gear, accelerate the car, or drive over a bump.


Leaks in or around your car are always a bad sign. The ML350 has oil-filled mounts that aid in vibration and shock absorption. Hence, whenever a mount breaks, it will cause the oil to leak.

If your ML350 is well maintained and has less mileage, you would hardly face any engine mounts. But in high mileage cars, the problem with engine mounts can come after 80,000 miles or so. To fix this issue, replacing the damaged engine mounts is the only option, requiring taking the car to the service station. 

3. Window Regulators Malfunction

Many owners report problems with the window regulators of their ML350. Although this is not a serious issue, if experienced, it would affect your comfort and peace of mind.

Like other modern cars, the Mercedes ML350 uses window regulators to aid the driver and passengers control the vehicle windows. The regulator, in general, consists of tracks holding the wheels inserted in the bottom of the window.

Suppose the regulator in any of the windows of your ML350 stops working. Then you will hear the motor working, but the window would be stuck. Moreover, you will hear a weird whining noise indicating a problem with the window in some cases.

Although the window regulator assembly in the ML350 comprises only two components – motor and regulator, fixing this problem can be complicated as it requires removing door panels, clips, rivets, and multiple other components. If you take your car to the service station, fixing this problem would cost around $350-$500 in the US.

4. Problem In The Suspension System

The suspension system in the ML350 is composed of innumerable small and large parts. Though many of these parts are immune to damage, a few suspension system components are not.

Worn-out shocks and struts are standard in the Mercedes ML350. Both of these components are essential parts of the suspension system. They aid in the car’s handling, comfort, efficiency, and performance.

While struts support the suspension’s structure, shocks, on the other hand, keeps the car from bouncing too much. Together these components restrict vibration and keep your ML350 up off the ground.

There is no proper schedule to replace the shocks and struts; many factors can influence the wear and failure of these parts. Some common symptoms indicating a problem with shocks and struts include – swaying, bouncing, or unusual rocking of your vehicle while riding or passing a bump.

Ideally, the suspension system requires attention after every 40,000 miles. Suppose you experience a problem with the shocks or struts or doubt the functioning of the suspension system of your ML350. Then going to the service station would be advisable. In some cases, other suspension system components like ball joints, tie rods, bushings, etc., might need repairing.

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