Most Common Problems of the Mercedes CLA & Its Worst Year

Most Common Problems of the Mercedes CLA & Its Worst Year

Just like any other car brand, Mercedes-Benz isn’t exactly flawless with every single model it puts out, and this is also true for the Mercedes CLA lineup.

As far as the Mercedes CLA goes, there are several common problems that both owners and automotive reviewers have reported that you should be aware of if you’re in the market for one.

Thus, we’ll be tackling each of those problems, the possible solutions for them, as well as the worst year of the Mercedes CLA that you should definitely avoid buying in this guide!

What are the most common problems of a Mercedes CLA?

Common problems of the Mercedes CLA include leaking injectors, gearbox oil leaks, the smell of burnt plastic from multiple possible sources, and the steering wheel turning to the right by itself.

The problems mentioned above are just a general summary of the issues you can expect to run into in the Mercedes CLA.

In the next part, we’ll be enumerating and discussing these problems one by one in order to find out what exactly causes them as well as how to resolve them.

Oil Leaking from Gearbox/Transmission

Oil Leaking from Gearbox/Transmission

One of the most common problems that owners have complained about on the Mercedes CLA is a gearbox or transmission that’s prone to leaking oil.

A very common symptom that points to a leaking gearbox is, of course, some puddles of oil pooling underneath the vehicle.

But since there are many different components of a vehicle where oil can leak from, you still need to verify this yourself by actually getting to the source of the leak.

A good place to start checking if the oil is actually leaking from the gearbox or transmission is the gearbox sump, which is usually an aluminum pan that acts as an oil storage.

However, there are other parts of the gearbox or transmission that are worth checking for leaks, as there is a chance that they’re actually the main culprit behind them.

The Mercedes CLA’s transmission/gearbox can leak oil due to the following reasons:
Seals or gaskets have been damagedTorque converters are malfunctioning (auto transmission only)Gearbox cap has not been tightened properlyDamage to the transmission oil sump/pan

The reasons we’ve enumerated can be quite tricky to trace back to if this is your first time experiencing a leak, so it’s highly recommended that you let a professional mechanic diagnose it.

To detect the leak more properly, the technician may remove the gearbox from the vehicle and disassemble it to look for any gaskets that are damaged.

While getting a new gasket doesn’t really cost that much, the time-consuming task of opening up the gearbox, replacing the gasket, and putting it back in the proper order can easily rack up the labor costs.

Furthermore, if it has been found that other major parts, such as the torque converter or transmission oil sump, are to blame for the leak, then get ready to spend up to $1,800 in total to replace them.


The good news is that this is only for the worst-case scenario, and there are still things that you can do to prevent the gearbox or transmission from leaking on the Mercedes CLA.

How to Prevent Transmission/Gearbox Leaks on the Mercedes CLA:
Follow the recommended gearbox oil change interval. Do not leave any remaining old gearbox oil when putting in new oil. Apply an oil seal additive to the gearbox seals to prevent them from wearing and drying up fast.

Leaking Fuel Injectors


Both gasoline (petrol) and diesel engine options of the Mercedes CLA can develop leaks in their fuel injectors, though this is a rarer occurrence compared to the leaks we’ve already discussed above.

But how can you tell if it’s the fuel injectors on the Mercedes CLA that are leaking? Well, we’ve listed their common symptoms below for you to keep an eye out for.

Mercedes CLA Leaking Fuel Injector Symptoms:
Drops of black oily liquid on the sides of the engine emission of black smoke from the exhaustRough or troubled engine idling

Since the fuel injectors of the Mercedes CLA’s gasoline and diesel engines are not interchangeable with each other, there is also a difference in the amount of injection pressure that makes one more susceptible to leaks than the other.

Comparing the Mercedes CLA’s two engine types, its diesel engine has a far higher injection pressure at 1,800 to 2,000 bars (26,000 to 29,000 psi) than its gasoline counterpart.

The CLA’s gasoline engine’s injection pressure doesn’t even come close to that at just a mere 3.5 (indirect injection) to 120 bars (direct injection).

Going by these numbers alone, it’s easy to see why the gasoline variant is not as prone to injector leaks compared to the diesel one.

But despite this, Mercedes CLA gasoline models belonging to the 2016 to 2020 model years have actually had a recall concerning the accumulation of debris in their fuel injectors.

Due to the trapped debris, the seal between the injectors and fuel rail can get damaged and cause fuel to leak from that point.

We’ll now be discussing other potential points to where the leak can originate from the injector and how to address each type of leak for both gasoline and diesel variants of the Mercedes CLA.

Mercedes CLA Gasoline/Petrol Engine Injector Leak

The gasoline-powered Mercedes CLA’s fuel injector can leak from the following areas:

  • Top of the injector (fuel rail connection)
  • Bottom of the injector (from engine junction)

There are two main locations where the injector leak can start on the Mercedes CLA’s gasoline engine, which is either at the top or at the bottom of the injector.

More specifically, a leak that originates from the top of the injector actually starts from where the injector connects with the fuel rail, which contains an O-ring.

Leakage from this portion can indicate that the O-ring that is designed to seal the flow of fuel through the injector has already been worn out or damaged.

Hence, simply replacing the leaking fuel injector’s O-ring will keep fuel and fuel vapor from escaping from the component.

As for leaks that originate from the bottom of the injector, they’ll specifically come from the junction where the injector connects with the engine block.

This end of the injector comes with what’s called a “Teflon seal”  that can also become worn out. Before putting on a new replacement seal, be sure to wipe the tip of the injector clean.


Mercedes CLA Diesel Engine Injector Leak

The diesel-powered Mercedes CLA’s fuel injector can leak from the following areas:

  • Injector inlet pipe (clamping point)
  • Injector return (potential O-ring or plastic tip issue)
  • Injector base (copper seal at engine and injector nose junction)

Fuel injector leaks that develop in the diesel variant of the Mercedes CLA are actually a bit similar to how they are for the gasoline variant, albeit there are now three leakage points you should keep in mind.

Injector leaks in the diesel engine can occur at the clamping point of the injector inlet pipe, as the pipe is known to get deformed through time under the engine bay.

Another potential source of the injector leak can occur as the fuel is recirculated back into the injector. 

Once again, another leaky O-ring is to blame for this, though it can also be accompanied by a leaky plastic tip at the end of the injector itself.

The third potential leakage point is at the base of the injector. More specifically, the leak can start from the copper seal at the junction where the engine and the injector nose meet.

Among the three types of injector leakage for the CLA’s diesel engine, leaks from the injector base are considered the most annoying to deal with due to the immediate onset of symptoms like compression loss and air noise.

In most cases, fixing injector leaks on the diesel-powered Mercedes CLA will require you to replace or repair the affected components of the injector.

However, since you are dealing with much higher injection pressure and overall compression in diesel engines, we recommend taking your vehicle to an authorized mechanic for any injector-related problems.

Burnt Plastic Smell

Mercedes CLA owners have complained of an unpleasant smell that is similar to burnt plastic while being inside the vehicle, though the source of this smell can actually come from multiple places not found in the cabin.

Overheated Transmission Fluid


One probable reason for the burnt plastic-like smell on the Mercedes CLA is that the transmission fluid or oil is already going bad, thus failing to do its main job of lubricating the transmission components.

The oil failing to lubricate the components properly means that it also cannot regulate the right temperature anymore, causing it to overheat and give off that burnt odor in the first place.

Instances like these basically tell us how important it is to make sure that you get your transmission fluid changed regularly.

Apart from emitting the smell of burnt plastic, old transmission fluid that excessively heats up can also prematurely wear all sorts of components in your transmission, thus potentially forcing you to burn a hole in your pocket too.

Exterior Body Panels Rubbing Against Wheel


Whether you’ve experienced a fender bender before or you’ve simply got a bolt loose on your bumper, any exterior body panel that repeatedly rubs against the tires of your car can also give off the smell of burnt plastic (or rubber, in this case).

Be sure to check underneath each of the wheel arches to see if there are any pieces of a body panel or fender liner that might be sticking out and have it replaced or restored back to its proper orientation.

Not only does this prevent the burning rubber smell, but it also saves your tires from wearing out prematurely or even blowing out while driving.

Of course, this means that you should also check the condition of your tires to see how all the rubbing has affected the treads.

Worn-Out Accessory Belt


Another culprit to the commonly reported smell of burnt plastic on the Mercedes CLA is a worn-out accessory belt, though it’s less frequent compared to the other culprits we’ve already discussed.

The accessory belt (also called the “serpentine belt”) is a rubber belt that transmits power to various accessories within the engine bay, such as the radiator, power steering pump, and AC compressor.

If the accessory belt gets too worn out over time, it will not be able to rotate properly around the different pulleys that it’s attached to.

This improper rotation will create friction between the pulley and the belt, causing the rubber material to excessively heat up and emit the burnt plastic or rubber smell.

Additionally, you may even hear a squealing noise from the engine bay due to the worn-out accessory belt.

After you’ve confirmed that the smell does come from the accessory belt, be sure to have it replaced right away before it gets worse and you end up having no AC on a hot summer’s day.

Worn-Out Hoses


The Mercedes CLA, just like any other vehicle, will have several hoses with different roles to play in its engine bay. However, these rubber hoses are notorious for wearing out prematurely and causing a burnt plastic-like smell of their own.

This can happen even if you don’t drive your Mercedes CLA that frequently at all.

The explanation for this lies in the settling of fluid that was once heated inside the hoses. If you haven’t used the car in a while, the fluid can slowly degrade the rubber material of the hoses.

The wear and tear on the hoses get further aggravated if you start using the car again and the fluid temperature rises up once more. Once the hoses get too worn out, they could completely break and cause the burnt plastic smell to arise.

This goes to show that your vehicle’s hoses are another thing that you should be adding to your long list of components to regularly check for wear and tear. If they are already worn out, then you know what to do (swap them out for new ones, of course).

The Steering Wheel Turns to the Right By Itself


A rather weird problem on the Mercedes CLA that may leave you entertaining the idea of poltergeists controlling your car is that the steering wheel seems to turn to the right without your input.

In reality, there’s not really any sort of paranormal activity that’s to blame for this phenomenon, as it’s been traced back to several issues with either the tires or the suspension components.

Uneven Tire Pressure


If your Mercedes CLA or any vehicle for that matter is slightly veering off to the left or right without any steering input, then there’s a chance that you have uneven tire pressure on one or several of your tires.

Even having one tire that’s a few psi lower than the rest can unbalance how the car sits on the ground, even more so when you’re out driving down the highway.

Apart from causing the car to slightly pull off to one side, uneven tire pressure also increases the wear that the tires go through.

With that said, make sure that all four tires have the same manufacturer-recommended tire pressure. 

Most modern Mercedes-Benz vehicles, including the CLA-Class, will come with a “Tire Pressure Monitoring System (TPMS)” that’s accessible via the Home button on the steering wheel and selecting the “Service” menu.

We recommend watching the short video tutorial below as a reference on how to access the tire pressure option on the Mercedes CLA (2019 model).

Faulty Shock Absorbers


Whenever any vehicle exhibits any kind of steering-related issue, it’s not a bad assumption that it may have something to do with the suspension components.

In the Mercedes CLA’s case, faulty shock absorbers have been found to be one of the most common reasons why the car slightly steers to one side.

Any change in the shock absorbers’ normal operation can alter your car’s ride height and handling, which may affect the car’s ability to keep straight in one direction.

As you can imagine, this can easily turn into a driving hazard if not resolved right away, so ensure that you get your shock absorbers checked and repaired by a professional mechanic.  

Bad Wheel Bearings


Wheel bearings are another kind of suspension component on the Mercedes CLA that are known to go bad and lead to the common problem of the car not going as straight as you want it to.

The wheel bearings connect the wheels to the car’s axle, so if they ever go bad or become faulty, you can expect that the wheel’s rotation will be affected and hindered.

The Mercedes CLA mostly exhibits this issue on the front wheel bearings, making the steering issue a bit more obvious than if it were to happen to the rear ones.

In addition, there are also other symptoms of bad or faulty wheel bearings that you should look out for, such as wheel vibration and wheel noises while driving.

In this case, simply having the wheel bearings replaced with a fresh set designed for the Mercedes CLA will keep it straight on the road and have you riding nice and smooth as well.

Worn-Out Silent Blocks


The silent blocks are another important component of the Mercedes CLA’s suspension system, and they’ve been known to go bad or “dead”, resulting in less stability and a tendency to turn to one side.

Silent blocks primarily absorb and dampen vibrations from the road, thus making the overall ride quality “silent” and comfortable.

Though once the rubber inserts in between the silent blocks’ metal bushings get too worn out, they will not be able to effectively mitigate all the bumps that you feel on the road and maintain steering stability.

If ignored, you’ll be left with silent blocks that are not so silent anymore and a car that seems to want to steer itself to the ditch on your right. It’s not the most pleasant-sounding scenario, we know.

This is why if you’re ever experiencing this steering issue, it’s also worth checking your silent blocks for any signs of wear and having them replaced when necessary.

What are the worst years of the Mercedes CLA?

The 2014 Mercedes CLA model year is considered the worst year for the car due to having the most reported problems, being the worst-performing Mercedes model for that year, and receiving low reliability ratings.


The Mercedes CLA’s model year run started from 2013 up until now (2023), and among those years, the 2014 model year did not perform up to the standards of its owners due to being riddled with issues.

For instance, the Mercedes CLA 250 model has garnered a total of 246 reported problems for 2014 alone, which accounts for about 57% of all total problems (428) reported for the model between 2013 and 2020.

Meredes-Benz CLA 250 Model YearNumber of Reported Problems

The nature of problems reported for the 2014 CLA model can vary from powertrain issues to problems concerning the steering, but its 5 most common problem categories are listed below.

Top 5 Problem Categories of the 2014 Mercedes CLA:
Engine/Engine Cooling – 57 Reported ProblemsElectrical System – 37 Reported ProblemsVehicle Speed Control – 30 Reported ProblemsEquipment – 29 Reported ProblemsElectronic Stability Control – 20 Reported Problems

Frequently Asked Questions (FAQs)