2015 Mercedes-benz C-class

Driver rear side rusted and cracked subframe.

I am filing a formal safety complaint regarding my 2015 Mercedes-Benz C300 (W205), with approximately 65,000 miles. An authorized Mercedes-Benz dealership diagnosed severe corrosion and perforation of the rear subframe and declared the vehicle undrivable due to this condition. The estimated repair cost is $5,531.53. The rear subframe is a critical structural component supporting the rear suspension. Its deterioration may compromise vehicle stability and potentially result in loss of control. I am extremely concerned that such a serious structural failure has occurred at relatively low mileage. Mercedes-Benz has extended rear subframe corrosion warranty coverage to 20 years with unlimited mileage for certain earlier C-Class models, but the W205 is excluded despite experiencing a similar problem. Mercedes-Benz USA denied my request for goodwill assistance. I respectfully request that NHTSA investigate whether premature rear subframe corrosion and perforation represent a broader safety defect affecting the W205 platform and whether a safety recall is warranted. The dealership’s diagnosis, repair estimate, and manufacturer correspondence are available upon request.

To Mercedes-Benz USA Customer Care, I am requesting a formal review and written explanation concerning case #24524936 and the approximately $6,000+ starter-wiring repair on my vehicle. Mercedes-Benz’s August 2017 recall notice for campaign 2017080002, NHTSA recall 17V114, states that the starting-current limiter can overheat under specified conditions, potentially causing surrounding components to melt and creating a fire risk. The notice further states that the authorized dealer will install an additional fuse in the electrical line to the starter at no charge. Because my vehicle has experienced burnt starter wiring, I request that Mercedes-Benz provide: 1. Written confirmation of whether my vehicle’s VIN was included in this recall. 2. The date and documentation of any recall remedy performed on my vehicle. 3. The technical findings supporting the determination that my starter-wiring damage is unrelated to the recall. 4. Confirmation of whether the starting-current limiter, additional fuse, and surrounding wiring were inspected. 5. A review of reimbursement eligibility and goodwill assistance for the repair expense. Please escalate this matter for technical review and provide a written response explaining the basis for the denial. If the matter cannot be resolved, I will consider submitting a vehicle-safety complaint to NHTSA. Existing case number: 24524936 Mercedes-Benz recall: 2017080002 NHTSA recall: 17V114

The contact owns a 2015 Mercedes-Benz C300. The contact stated that while driving at an undisclosed speed, there was an abnormal sound coming from the vehicle and the vehicle became difficult to maneuver. The failure had occurred on several occasions. The vehicle was taken to an independent mechanic where it was diagnosed that there was two large holes and rust located on the rear subframe, an unknown part needed to be realigned and needed to be replaced. The vehicle was towed to a dealer where it was confirmed that the rear subframe and another unknown part needed to be replaced. The manufacturer was notified of the failure by phone and stated that the vehicle was not under warranty. The failure mileage was approximately 120,000.

The rear subframe on the car is rusting badly and the Mercedes certified mechanic states that the entire frame needs replacement. With braking, the car could fishtail and be in a serious crash. The two model years prior to mine have had similar problems and a recall has been established for those years. I am asking the NHTSA to work with Mercedes-Benz to establish a recall for the 2015 C class before someone is injured as a result of this defect.

The vehicle’s rear subframe has become severely rusted and structurally compromised. This failure has caused the vehicle to pull sharply to the right when the brakes are applied. The rear subframe and affected components are still on the vehicle and are available for inspection upon request. This condition creates a serious safety risk because the vehicle can suddenly pull hard to one side during braking, making it extremely difficult to maintain control. At highway speeds or during emergency braking, this could cause the driver to lose control of the vehicle, leave the roadway, collide with another vehicle or object, or potentially result in a rollover. The failure is especially concerning because it directly affects the stability and braking behavior of the vehicle. The problem was inspected and confirmed by Mercedes-Benz of Durham. The dealer determined that the rear subframe was severely rusted and that this condition was responsible for the vehicle pulling strongly to the right during braking. The vehicle has therefore been inspected by an authorized Mercedes-Benz dealership. The condition has not, to my knowledge, been inspected by police or insurance representatives. There were no warning lights, dashboard messages, or noticeable symptoms indicating that the rear subframe was deteriorating before the problem became apparent. There was no advance warning that the subframe had become severely rusted. The issue only became evident when the vehicle began pulling sharply to the right under braking. Because there were no warning signs before the failure, I believe this condition presents a significant safety hazard. A driver may continue operating the vehicle without knowing that the rear subframe has deteriorated to the point that vehicle stability and braking control are affected.

I noticed some unstable braking at higher speeds. I took the vehicle to a mechanic and he discovered severe rust with perforation of the rear subframe "very near to where some of the suspension connects to it and is allowing a lot of extra movement, especially under braking." He told me that the vehicle was unsafe to drive on the highway or at speeds over 40 mph and should be repaired, preferably through Mercedes as soon as possible. I've reached out to Mercedes Benz USA. They told me that this has been a common problem and some vehicles have had the warranty extended because of it. My vehicle is not included in the warranty extention but they suggested that it may be eligible for a "goodwill" repair. I've reach out to my local Mercedes dealership to further investigate the problem and are awaiting a return call.

The rear structural subframe on my vehicle has experienced severe, premature corrosion perforation (rotting from the inside out), resulting in a major compromise of the vehicle’s structural integrity. This subframe is a critical safety component that supports the entire rear suspension, differential, and braking components. The subframe has rusted to the point of developing holes and structural cracks under normal operating conditions. This severe deterioration creates an immediate safety hazard, as a total failure or snapping of the subframe while driving can cause a sudden loss of vehicle control, unpredictable suspension geometry changes, and a severe risk of a high-speed crash.Mercedes-Benz has previously acknowledged an identical, widespread manufacturing defect and issued an extended 20-year warranty (NHTSA ID NCU-2023020004) for older model lines (such as the W204 and W212). However, my specific vehicle is currently excluded from that extension, despite suffering from the exact same premature metallurgical failure and safety risk. The deterioration is identical to the covered models, where road debris and water get trapped inside the hollow subframe unit, causing it to oxidize and disintegrate undetected from the interior until structural failure occurs.This constitutes a severe safety hazard. Driving with a compromised rear subframe risks a catastrophic detachment of the rear axle, control arms, and braking lines while at highway speeds. A sudden failure will lead to immediate loss of steering control and an incredibly high probability of a severe motor vehicle accident, endangering lives. I am filing this complaint to urge the NHTSA to investigate Mercedes-Benz and mandate an extension of the existing warranty framework to cover newer model years that exhibit the exact same premature corrosion failure. Dealers are denying coverage based on arbitrary VIN cutoffs, forcing owners to drive unsafe vehicles or pay out of pocket for a known structural defect.

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.

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.

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 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.