What 584 owners told NHTSA about the 2012 Mercedes-benz C-class Coupe

2012 Mercedes Benz C300 4-Matic; Failure of rear subframe, significant crack of an important support member; very limited minor corrosion of the other parts of the frame, seems to be a manufacturing quality defect in a very specific part. Vehicle has been inspected by a highly qualified independent mechanic and by the closest manufacture's dealer in Massachusetts. Car cannot be driven because it is unsafe to do so. Both the dealer's service department and the independent repair shop have advised and confirmed this. Limited research online seems to indicate that this problem is well known by Mercedes Benz, and the manufacturer has issued recalls in other countries and has taken some responsibility for this defect. However, in the USA, Mercedes Benz has not issued a recall, to the best of my knowledge. It certainly seems that they should have done so. It is highly likely that many owners with this problem lack the knowledge or experience needed to report this problem to the appropriate authorities. I happen to have an above average knowledge regarding automobiles. I first became aware of this problem in Nov., 2021. The vehicle is available for inspection by your department if you deem appropriate.

NHTSA ODI 11477837

The contact owns a 2012 Mercedes -Benz C300. The contact stated that upon inspection of the vehicle, he was informed that corrosion had developed on the subframe. The dealer informed him that the subframe needed to be replaced to prevent a possible severe safety failure. The contact emailed the manufacturer about the failure and received a response informing him that they could not offer any assistance. The manufacturer referred him to the NHTSA for additional assistance. The vehicle had yet to be repaired. The failure mileage was approximately 113,000.

NHTSA ODI 11476904

The contact owns a 2012 Mercedes-Benz C300. The contact stated that while her granddaughter was driving the vehicle, there was a rattling sound coming from underneath the vehicle. The vehicle was later inspected by an independent mechanic who diagnosed that the rear passenger’s side wheel well had sustained severe rust and corrosion and informed the contact that the vehicle was unsafe to be driven. The vehicle was not yet repaired. The manufacturer and local dealer were not notified of the failure. The VIN was not available. The failure mileage was 115,000.

NHTSA ODI 11475858

The contact owns a 2012 Mercedes-Benz C300. The contact stated while driving approximately 2 MPH over a speed bump, there was a loud cranking sound coming from the vehicle. There were no warning lights illuminated. The vehicle was taken to the local dealer and diagnosed with failure to the rear subframe due to severe rust. The vehicle was repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 121,218.

NHTSA ODI 11475116

My car smell like a gas leak. I had went to a car shop to have the car to looked at. The mechanic had told me that the fuel filter flange is leaking gas.

NHTSA ODI 11474194

So here I am - another "happy" driver with a rotten subframe. Started noticing instability on the highway speeds a few months ago. Cracking noises lately. Since I use this car my very honest mechanic immediately told me that my rear subframe is completely done and I should not be driving the car until it is replaced. He quoted me $4500 (OEM parts + labor), but suggested that I take my car to MB and insist on covering the repair costs as this issue did not seem typical to him at all. I started googling and ended up here. Seems like this is a common issue and sounds like MB will replace the subframe for free in some other countries (cananda and Germany, .The dealer said the repair will cost Over $5000.00 This is a safety issue, A real big one. And the fact it's covered in other countries is so not fair. I own another mercedes and now I feel the cars are not as safe as they used to be. Please let me know what I need to do next

NHTSA ODI 11473597

The rear sub frame has rusted out and broken causing the car to veer suddenly to the left during braking. A quick search of the internet reveals that this is a common problem with this car. The dealership has quoted me $4,000 for the repairs.

NHTSA ODI 11472766

The contact owns a 2012 Mercedes-Benz C350. The contact stated while driving at an undisclosed speed, the sunroof glass shattered and landed on the sunroof cover. There was no impact on the sunroof that could have caused the sunroof to shatter. The contact and his daughter did not sustain any injuries. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 75,000.

NHTSA ODI 11471965

I was traveling at roughly 55mph when I had to make a sudden deceleration due to another vehicle pulling out in front of me. When I applied the brakes, the car unexpectedly pulled violently to the left nearly causing a head-on collision with an on coming vehicle. After Googling the symptoms/scenario, I found that this can be caused by a rusted and failed rear suspension subframe. The control arms for the rear wheels become detached from the subframe as a result. Based on my research, this seems to be an extremely common occurrence. So much so that Mercedes Canada and Mercedes Germany are replacing the defective subframes free of charge as they’ve concluded the cause to be “inadequate corrosion protection” applied to the inside of the subframe. It seems as though they’re rotting from the inside out. After learning everything about the issue, I pulled my car on to ramps in my garage and was able to confirm that my subframe had indeed failed. This is a serious safety issue which is being addressed elsewhere. During my research I was unable to find a recall or TSB related to this issue, only hundreds of people stating that Mercedes forcing customers to cover the cost to repair this extremely dangerous manufacturing defect.

NHTSA ODI 11471671

Rear Subframe Rot- this seems to be a common and known issue with Mercedes’ that should be a recall. Yet Mercedes is charging almost $6000 to get this fixed at the dealer. Plus the parts are on back order for months. This is causing cars to sway when stopping. This is definitely a hazard and should be addressed ASAP!

NHTSA ODI 11470493

The rear subframe on my 2012 Mercedes Benz C300 was corroded and broke. This caused the car to lose control and easily could have been been life threatening at high speeds. Mercedes Benz is clearly aware of this issue and knows this is a part defect but has not been willing to do a recall in the US even though they have done so in other countries. The dealership has told me this needs to be repaired as the car can’t be driven, so I am not happy I need to pay $5,000 out of pocket for a part defect Mercedes knows about and refuses to issue a recall even though this problem can cause a fatal accident. There were no warning signs besides hearing thumping sounds and the instability caused by the part defect when it finally failed and broke.

NHTSA ODI 11468798

AUTO IS LESS THAN 100K MILES EXCELLENT CONDITION HAD THE TURBO GASKET GO BAD ON THE AUTO. OIL LEAKING IN THE MAIN ENGINE COMPARTMENT AND ON GROUND DUE TO THE GASKET ISSUE. COULD CAUSE DAMAGE TO ENGINE AND TURBO. GASKET SHOULD NOT HAVE GONE BAD. WHILE AT THE MECHANICS SAME ISSUE WITH THE SAME EXACT MODEL OF MERCEDES, NOT SURE THE YEAR BUT IDENTICAL BODY STYLE. REPAIRS WERE COMPLETED ON 06/07/22 COST THROUGH MECHANIC $465.00 ANY TIME DUE TO PASSING OR EXCELARTION THE ENGINE WOULD MISS OUT AND LOSE POWER FOR THE PASSING OR ESCELARTION.

NHTSA ODI 11468165

Part number: 207-350-97-02 This is the sub frame part number, during routine maintenance i found a cracked rear sub frame mount. Upon googling, there are hundreds of owners with that same problem. Cars with milage ranging from 40,000-150,0000 with the same issue. Under hard braking the car is unstable. When I called the MB dealer to inquire about the problem they did confirm that the problem is known but is not a safety recall and the repair bill is near $5,000. So Mercedes, confirmed it’s a known issue with a faulty part, confirmed it was a safety issue with the 2008-2012 Mercedes c300 and is not covering it.

NHTSA ODI 11467644

The contact owns a 2012 Mercedes-Benz C300. The contact stated while driving 70 MPH, there was an abnormally loud sound from the rear of the vehicle. The contact lost control of the vehicle. There was no warning light illuminated. The contact was able to continue normal driving once he regained control of the vehicle. The contact scheduled an appointment with an independent mechanic for the vehicle to be inspected. The contact was informed that the rear subframe had detached from the passenger’s side of the vehicle due to severe corrosion. The dealer was notified of the failure and informed him that there were no recalls related to the failure on his vehicle. The manufacturer was not notified of the failure. The vehicle was not repaired. The failure mileage was approximately 138,000.

NHTSA ODI 11467139

The contact owns a 2012 Mercedes-Benz C300. The contact stated that while the vehicle was receiving a routine maintenance, she was informed that the rear sub frame was rusted and had two holes. The vehicle was diagnosed that there was a transmission leak and the rear sub frame needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure but no additional assistance was provided. The failure mileage was approximately 88,000.

NHTSA ODI 11464082

Major rust in the welded joints of the Steel subframe. Long crack development along the seams, could have led to catastrophic lost of control of vehicle if the breaks were not found. This is an apparent flaw with the C-Class Mercedes Benz and quite surprising to the Service Reps at my dealership that this has not been a recall issue, as they’ve replaced many. The repair is quite costly, over $5,000. There were no symptoms, warnings or messages. This was found when the vehicle was in for a 10k service. I have a video sent by the technician that show the inspection of the vehicle.

NHTSA ODI 11463883

The contact owns a 2012 Mercedes-Benz C300. The contact stated while driving approximately 65-70 MPH, he heard abnormal clicking sounds coming from the rear of the vehicle. Additionally, the contact stated that while driving and depressing the brake pedal to come to a complete stop, the vehicle swerved while stopping. The vehicle was taken to an independent mechanic where it was diagnosed that the rear driver's side subframe was severely corroded and fractured and needed to be replaced. The dealer was notified of the failure and informed the contact that the vehicle would be repaired at his own expense. The vehicle was not repaired. The manufacturer was notified of the failure but did not provide any assistance. The failure mileage was approximately 75,000.

NHTSA ODI 11463118

The rear K frame on Mercedes Benz C300 totaly rusted through and broke apart causing the entire rear of vehicle to rest upon the fuel tank. The failure also caused stress on rear brake lines. The vehicle is 10 years old with 90,000 miles purchased brand new and garaged. Mercedes has performed a recall on Canada vehicles but no USA vehicles. This is total negligence. This is going to cause a fatality. Either a vehicle will catch fire or brake lines will fail and cause an accident. The vehicle is known by the dealers to have this damage/failure. I googled and found numerous cases. Mercedes was not willing to stand by the vehicle and repair. This should be a recall like it is in Canada. I was quoted $5000.00 to repair by Mercedes.

NHTSA ODI 11462469

I drove over an object on the highway and noticed my car veering left and wobbly when turning. A week after, it is squealing like a load of piglets in my trunk whenever I go over a bump, then my battery light came on and I took it to the shop and contacted my insurance, who denied my claim saying it was 'wear and tear'.

NHTSA ODI 11459967

From the mechanics notes: Four-wheel alignment could not be completed. Attempts to align the rear axle were unsuccessful due to flexing/movement in the rear suspension. A brief road test revealed occasional suspension “clunking” coming from the rear of the vehicle. Close examination of every suspension component mount revealed heavy cracking on the passenger side lower drag link subframe mount (see emailed image). The driver’s side low drag link mount location is also starting to show signs of overstress and rust/flaking. This is a known design defect that has been the subject of a manufacturer’s recall in Canada. Given the substantial safety impact of this design defect/failure, it is expected that a US recall will be forthcoming. Proper repair of this failure involves removing the entire rear axle/subframe assembly and either rebuilding/re enforcing the subframe or replacing it with a new unit and transferring all the suspension components to the new subframe. A current check of subframe availability is showing NLA (no longer available) status from Mercedes wholesale dealers – likely due to recent high demand and inability to satisfy that demand. This supply issue may also be playing a role in Mercedes’ failure to address this high level safety issue with a US based recall campaign. The manufacturer may be ramping up production of this component to address anticipated need – waiting to announce a recall when it has sufficient parts on hand to execute the campaign. It is strongly recommended that you file an NHTSA complaint for this issue and limit driving until the problem is rectified either independently or under the auspices of a recall campaign. The passenger side rear drag link has not yet completely separated from the subframe but is likely to do so soon which can result in an accident or loss of control as this critical suspension link is responsible for maintaining steering direction of the right rear wheel.

NHTSA ODI 11458128

I took my vehicle in for a state inspection and was informed the rear subframe was rusted/rotting and on the verge of detaching. Had this happened while driving, the results could have been catastrophic. The vehicle cannot be driven until this $4K dollar repair is completed. Upon speaking with the mechanic, this is a well known issue within Mercedes. Had I not asked for an alignment, this would have remained undiscovered until it inevitably broke off while driving the vehicle. This is a major safety issue and a safety recall should be issued.

NHTSA ODI 11456960

The contact owns a 2012 Mercedes-Benz C300. The contact stated that while driving at an undisclosed speed, he depressed the brake pedal and the vehicle swerved. Upon inspection, the contact noticed that the rear passenger's side sub-frame was corroded and the stabilizer arm had detached from the sub-frame due to corrosion. The vehicle was taken to an independent mechanic who diagnosed that the sub-frame needed to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 100,000.

NHTSA ODI 11456741

Vehicle was in for state inspection at an authorized inspection station. It failed inspection due to severely rusted and deteriorated rear K-Frame which had to be replaced to pass inspection. This is a major defect I feel caused by manufacture negligence. There were no warnings, messages or any signals indicating a problem. This issue could have severely caused an injury or even death had it not been detected by the mechanic inspector. Mechanic stated to me that he had replaced several of the rear K-Frames in the last year on this make and model.

NHTSA ODI 11456652

While driving recently we noticed that the vehicle pulled to one side while braking, and very hard under quick stop tests. Vehicle handling felt extremely dangerous when performing a hard brake test. An inspection was performed, and the service center found a rotted out rear subframe, and cracking around the suspension mounting brackets. After researching this repair, we found this to be a common problem in this and similar model Mercedes-Benz (MB) vehicles of that vintage. I understand that a recall may have been issued in Canada regarding this issue, but not in the U.S. Mercedes-Benz and their service stations have acknowledged this issue is common but they have not taken action to rectify this serious problem, or to compensate owners for the repair costs, which range from $3500 to $6000 depending on where the vehicle is serviced. We are the first owners of this car. It is barely 10 years old, is regularly maintained, and thoroughly washed during the winter months to remove road salt. A well maintained vehicle should not deteriorate this rapidly from rust, especially a Mercedes-Benz. We feel that it is unacceptable for MB to remain unaccountable for this problem.

NHTSA ODI 11455453

Rear subframe failure caused me to loose control of vehicle almost resulting in a serious highway accident. Rear driver side stabilizer subframe mount was completely corroded and broken away from the subframe. There is no other significant corrosion on the subframe. MB claim normal corrosion however the pictures tell a different story.

NHTSA ODI 11454235