2015 Mercedes-benz C-class

I am reporting a potential safety defect involving the locking/key-detection system in my 2015 Mercedes-Benz C300. On [XXX], at approximately [XXX] p.m. in Coral Ridge, Fort Lauderdale, I secured my young son in his car seat. My purse, containing the key fob, and my phone were on the front passenger seat. I closed the door and walked around to the driver's side. The vehicle had locked all doors by itself. I did not press the lock button or intentionally lock the vehicle. There were no warning lights, messages, alerts, or other symptoms beforehand. My [XXX] son was trapped inside the locked vehicle, and both my key and phone were also inside, leaving me unable to access him or call for help. I flagged down a passing car, and we ultimately had to break a window to reach him. The vehicle has not been inspected by Mercedes-Benz, a dealer, police, insurance, or an independent service center, and the issue has not been reproduced or confirmed. After replacing the window, I have not attempted to recreate the incident because of the safety risk. The vehicle remains available for inspection upon request. I am concerned that the vehicle can lock with the key fob inside the passenger side, creating a potentially serious risk if a child or vulnerable occupant is trapped inside, particularly in hot weather or where immediate assistance is unavailable. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2015 Mercedes-Benz C300. While the contact’s son was driving approximately 20 MPH, the vehicle veered to the left and into the next lane when the brake pedal was depressed. The vehicle was cautiously driven back to the residence and parked. The vehicle was later towed to the local dealer to be diagnosed, and it was determined that the rear subframe had severe rust and was fractured and needed to be replaced. The vehicle was not yet repaired. The manufacturer was notified of the failure, but no assistance was provided. The contact was informed that the vehicle was not covered under the manufacturer’s extended warranty coverage for the failure. The failure mileage was 110,000.

I am a mechanic speaking on the behalf of a customer; this customer is experiencing problems with her rear subframe. The older generation of her car has a famous issue with rear subframe rusting out. Her car uses an updated part number that is almost identical in construction to the failure prone part that was famous for rusting out, although they are NOT the same number. The failure prone number is 2123503805 or 2043500141, they are installed on the older chassis, w204, w212, etc. The part that is in THIS vehicle is 2123503605, the construction is almost identical to the part numbers listed for the w212 and w204 provided above. There is no drainage holes provided for water that has entered through rain or any other detritus that will permeate on the road's surfaces through natural progression of the vehicle's life, like on the older chassis. The material used is steel with paint on the outside instead of some sort of encapsulation that coats both inside and outside surfaces. And because these don't have any sort of ability to evacuate any substances, they are interacting with unprotected metal and will react into rust. This failure can lead to misalignment at the very minimum of problems, at the worst, it can cause control arms falling off, causing wheel hub assemblies to fall off, this shouldn't have to be explained but this can cause major injury or death, not only to the passengers to the vehicle, but to others who share the misfortune of being at the wrong place at the wrong time. And, the understanding of these not being the SAME part shouldn't warrant the extension of the recall to these particular vehicles, but the failures are similar to what was seen before on other older vehicles and should warrant further investigation. With hope, this could just be an isolated incident, but since patterns are uncanny, this should be investigated with some interest to the public wellbeing. Cordially Naseam F. Samaan Licensed Virginia State Inspector. Sanko Auto Care

Vehicle rear subframe has rusted through, causing vehicle to swerve upon braking, making the car unsafe to drive for the occupant, other vehicles on the road, and pedestrians. Mercedes dealer has advised that subframe has rusted through, requires replacement. The car will be brought to the dealer for repair (at owner's expense) by Friday, 8/28/2026. We can request that the dealer provide us with the subframe - please advise. The vehicle provided no warning indications.

An inspection of my vehicle on August 6, 2026 disclosed that the rear subframe has corrosion, including perforation. It is my understanding that this problem has been identified in mine and many other Mercedes-Benz models, and that Mercedes-Benz has offered an extended warranty to replace the subframe in certain of these models, but my model for the year it was manufactured was not included. I was not made aware of this potential problem by Mercedes-Benz, and they are not offering an extended warranty to resolve this serious safety issue.

The contact owns a 2015 Mercedes-Benz C300. The contact stated that while driving at various speeds and depressing the brake pedal, the vehicle fishtailed on several occasions. The vehicle was taken to an independent mechanic, where it was raised on a lift, and the mechanic discovered that the rear subframe was severely corroded. The mechanic determined that the failure was associated with Manufacturer Communication Number: MC-10232321 (Structure); and referred the contact to a dealer for assistance. The vehicle was towed to the dealer, where the failure was confirmed, and it was discovered that the rear subframe had separated. The dealer informed the contact that the vehicle was unsafe to drive. The contact was provided an estimate for the repair and was informed that goodwill assistance would not be provided. The vehicle was not repaired due to the cost. The manufacturer was notified of the failure and informed the contact that the dealer was unreachable. The failure mileage was approximately 120,000.

During a mandatory Virginia State Safety Inspection, the vehicle failed due to severe structural corrosion and perforation of the rear subframe. Because these components notoriously corrode from the inside out, the fact that the rust is externally visible and structurally failing indicates an advanced, catastrophic material breakdown.The rear subframe serves as the foundational load-bearing anchor for the rear suspension and control arms. This level of structural rot poses an immediate, severe safety hazard. Had the failure occurred while driving at highway speeds rather than being caught during an inspection, the suspension mounts could have catastrophically detached, causing a sudden loss of vehicle control, unpredictable fishtailing, and an imminent crash risk. There are absolutely no dashboard warning lights, diagnostic trouble codes (DTCs), or driving indicators to alert the driver of this structural degradation. The defect remains entirely hidden until the metal physically fractures or the vehicle fails a professional inspection. Furthermore, because neighboring states (such as Maryland) do not mandate annual safety inspections, this severe structural failure will go entirely unnoticed by thousands of drivers until a catastrophic on-road failure occurs. Mercedes-Benz has already explicitly acknowledged this exact engineering and material defect in the preceding W204 generation (C-Class models up to 2015), subsequently issuing a 20-year, unlimited-mileage extended warranty for rear subframe corrosion. However, Mercedes-Benz has arbitrarily excluded my 2015 W205 C-Class model from this coverage, despite the vehicle employing a highly similar subframe design that suffers from the exact same moisture-trapping and premature rotting failure mechanism. This represents an unaddressed, systemic manufacturing defect that poses an immediate risk to public safety. I’ve included two photos showing holes in the subframe from rusting inside out.

Rear subframe rust has deemed the car unsafe to drive. Hitting a pot hole at high speed or any sudden stop could cause the subframe to collapse causing loss of control of car. Car is available for inspection upon request. Car was taken in for regular oil change and multi-point inspection when rust was noticed by mechanic at the dealership. Car is located in East TN not the snow belt. There have been recalls on similar models for the year prior, but this vin is not part of the recall and has same issue, although the number 204 which is part of the recall is stamped on the part. (Pic attached below.)

The contact owns a 2015 Mercedes-Benz C300. The contact stated that while the vehicle was parked, the contact became aware that the panoramic roof failed to close as intended. The vehicle was taken to the dealer, where it was determined that the panoramic roof guide rails had failed. The contact was informed that the panoramic roof guide rails needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure, and a case was filed. The contact was informed that the mileage and age of the vehicle had exceeded the limitation. The failure mileage was approximately 110,000.

The sunroof panel being cracked on this car is a well known and documented issue. There have been several recalls for it just not on my specific model. Yet I’m just like them, stuck with a broken in half sunroof panel that let water seep in and ruin my sunroof twice now, and the only fix is to pay $4500. This is insanely high for the small panel I’m talking about.

Sunroof Glass failure vin:55SWF4KB1FU039607 2015 Mercedes C300 2PM July 16 2026, Tampa highway near college park east coordinates28.06840 N.82.35292W TEMPERATURE 91F

Car was pulling to one side. Replaced the front routers and breaks. Problem still persisted. After more investigating the subframe was found to be rusting out, Mercedes of New London CT said it was unsafe to drive. But allowed my daughter to drive it home. This car was purchased it brand new from Mercedes=Benz of Warwick. The car was garaged all it life. This should not happen. They have had recalls and problems with this model just not this one. My concern is the safety of those driving this model clearly the problem was not solved. Please make Mercedes notify people driving this model, that there is a known subframe corrosion issue.

My 2015 C300 W205 failed at its state inspection today due to a rusted through rear subframe. I understand that the W204 warranty on this was extended to 20 years/unlimited miles but the W205 was not. I have contacted Mercedes customer care for a potential goodwill repair since this seems to be a known issue with class actions pending. This should not be failing and it’s unclear why Mercedes did not include all models with the same design in its extended warranty. The costs could be up to $7k.

The contact owns a 2015 Mercedes C300. The contact stated that the driver's side rear brakes and rotors were rusted. The contact stated that when the brakes were applied, they were slow to respond. The TPMS warning light was illuminated. The vehicle was taken to a braking center, which declined the warranty for the aftermarket parts. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not notified. The approximate failure mileage was 176,000.

The car would seem to shift when stopping , when tires were removed the rear subframe had rusted out completely, this is a major safety issue and could cause loss of control of the vehicle. The failure is the same as what the w204s experienced but they’re being fixed at the cost of Mercedes

I was driving my car was sputtering or trying to shut off while I press the gas and I let go of the gas and it catches and stayed on. I took it to the dealership and they said they found nothing wrong. May 3rd around 12pm im driving on the freeway and as im getting on the express lane going 60 it dies and I couldn't move the steering wheel and I slammed into a guardrail. After doing research my car (vin [XXX] ) had multiple recals from the fuel pump and steering wheel and the dealership never fixed or checked any recalls before selling it to me. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Component/System Failure: The rear subframe on my 2015 Mercedes-Benz C300 failed due to severe corrosion/rusting. The subframe is available for inspection upon request. Safety Risk: This failure created a serious and immediate safety hazard. While driving at highway speeds, the structural integrity of the vehicle was compromised, I had to break and lost control of the vehicle and almost causing a crash. This also posed a danger to other drivers on the road. The condition was severe enough that I believe I narrowly avoided a major accident. Confirmation of Problem: The issue has been confirmed by a Mercedes-Benz dealership service department, who identified the subframe as rusted and structurally compromised. Inspection by Other Parties: The vehicle has been inspected by a Mercedes-Benz dealership. It has not yet been inspected by the manufacturer directly, police, or insurance representatives. Warning Signs Prior to Failure: There were no clear warning lights or dashboard messages indicating this issue prior to the failure. The problem appears to have progressed without visible warning until it became severe. Additional Context / History: Mercedes-Benz has acknowledged subframe corrosion defects in certain vehicles from approximately 2010–2020, but my specific vehicle was not included in the extended warranty coverage. This is the second Mercedes-Benz vehicle I have owned (previously a 2012 model) that has experienced the same subframe failure. I was previously told that this issue had been resolved in newer models, which influenced my decision to purchase this vehicle. Additionally, this vehicle was purchased as a Certified Pre-Owned Mercedes-Benz, which implies it passed a detailed inspection process. Despite this, a major structural component failed. A warranty claim was submitted but denied on the basis of “rust,” even though this appears consistent with a known factory defect.

The rear of the car would begin to slip during turns and when brakes were applied. When I had the issue checked out, my mechanic said that the rear subframe has severe corrosion, rust and holes. The subframe perforation is causing instability in the rear wheels, which is a safety issue. I took the car to Mercedes for an inspection and they confirmed the holes in the sub frame,with the inspector stating that the sub frame is "about to fall off". I believe this to be a safety issue as having the wheels or subframe fall off could cause fatalities. This appears to be a manufacturing defect given recalls for the same issue in other models of the 2015 c300. See video of the inspection of my car here: [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

rusted rear subframe. unsafe braking and suspension due to this. damage code 35441 47 shows 2008-2015 vins but my vin does not show active recall, yet has the issue

Mercedes issued a recall for Mercedes C class for the model year up to 2015 for rear subframe that is rusting with holes in it. The dealer tells me my car is not covered by Mercedes even though it is a 2015 model. They gave me an estimate for the repair of over $5000. They say the model changed mid 2015 and mine is a model that is not covered. This could cause a serious crash at high speed. I am not sure why that repair is not covered for my 2015 model & I would like Mercedes to honor the repair.