2020 MERCEDES-BENZ GLC 300 Complaints

My 2020 Mercedes-Benz GLC 300 experienced a complete engine failure at ~51,000 miles, shortly after a major repair for a known defect. Initially, the vehicle showed a misfire on cylinder #3, which was diagnosed at RBM of Alpharetta as low compression due to valve seat damage, matching MB TSB LI01.30-P-072328. The cylinder head was replaced in Aug 2025. About two months later, while driving under normal conditions, the vehicle made a loud cranking/knocking noise and completely stalled in traffic without any check engine light or warning. This sudden stall posed a serious safety risk. The vehicle was towed to the same dealer, who has now diagnosed the engine as fully seized and recommended a complete engine replacement. I had also completed the 50,000-mile scheduled service at the same dealer shortly before this failure. Despite this being clearly linked to a known design defect, Mercedes-Benz USA has declined to provide further assistance or goodwill coverage. I am reporting this to highlight both the mechanical failure and the safety risk—this engine seizure occurred without any prior warning lights and could have resulted in a crash. I believe this reflects a systemic failure with the M264 engine in GLC 300s, affecting vehicle reliability and road safety. MBUSA has not provided a written explanation for their denial. I am concerned this issue may affect other GLC 300 owners and deserves investigation or recall consideration.

I am the owner of a 2020 Mercedes-Benz GLC300 with the M264 engine. I am hoping that you can assist me with a widely reported, systemic defect: the premature failure of the master cylinder, regardless of vehicle mileage. This issue is extensively documented by numerous owners of the 2020 and 2021 GLC300 models across various public forums, including Reddit and dedicated GLC owner communities. I took my vehicle to Mercedes dealearship for annual service and an intermittent check engine light. The dealership informed me it was a spark plug issue. Once repaired the check engine light went on permanently and the car hesitated as if it would turn off. I brought my car in for service and was told that it was a master cylander failure of the engine. Known Defect: The defect is so widespread that it indicates a manufacturing or design flaw. Corporate Refusal: Mercedes-Benz corporate has failed to acknowledge this systemic issue publicly or initiate a recall. Local Acknowledgment: When engaging with Mercedes-Benz of Paramus, Service Manager Ben Wright acknowledged both the existence of the issue and Mercedes-Benz's corporate awareness of the defect, yet confirmed the lack of a formal recall. Repair Cost & Offer: Following the failure, I was presented with a $12,000 repair bill for parts and labor. The only offer of assistance from corporate was a minimal 20% discount, still forcing me to pay a final cost of $10,620 for a repair that should be covered under a mandatory recall. Unfortunately, I was out of warranty by 1 year and 8,000 miles. This refusal to address a known mechanical flaw is unacceptable, especially given the significant financial burden placed on owners for a defect acknowledged internally.

Problem (repeat failure / prior warranty replacement): This vehicle has a recurring headlamp defect involving moisture ingress into the headlamp housing/connectors, causing electrical shorting and warning messages, with risk of headlight failure. Mercedes-Benz replaced this same headlamp under warranty in 2021 for the identical issue (moisture/shorting). The defect has recurred on the same vehicle.Recent verification: On Oct 13, 2025, the dealer (Mercedes-Benz of North Palm Beach) observed visible condensation/fogging in the lamp and confirmed it matches the prior failure that was repaired under warranty. Pattern affecting other owners: There are multiple consumer complaints in NHTSA’s database describing condensation, moisture intrusion, shorting, and headlamp malfunctions on GLC vehicles, including the 2020 model year. This indicates the issue is not isolated. Related recalls / known condition: NHTSA Recall 22V261 (GLC) identifies headlamp moisture/connector sealing problems leading to lighting failure. While my VIN is not currently included, the failure mechanism is the same: moisture ? short ? potential loss of headlight illumination. There are also GLC lighting recalls addressing exterior lighting malfunctions, underscoring that lighting faults on this platform are safety-relevant. Safety risk: Headlamp moisture/shorting can disable exterior lighting, reduce nighttime visibility, and increase crash risk. This is a repeat, safety-related defect previously repaired by Mercedes-Benz that has returned. Requested action: Please investigate this headlamp moisture/shorting defect on the 2020 GLC as a recurring safety problem, consider expanding applicable recall/remedy coverage, and direct the manufacturer to provide a durable fix and appropriate remedy for affected vehicles.

The engine is failing, I was on my way to drop my [XXX] off at daycare when suddenly my car went above and stayed above 5rpms meanwhile I was only able to drive 8mph. This caused a tractor trailer swerving into on coming traffic, if he didn’t my toddler and I would have been killed. As I managed to pull off and call my husband to get the baby the engine started making a strange clicking noise. There’s maybe 60,000 miles on this vehicle none of this should be happening. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

On August 15, 2025, I was driving my Mercedes-Benz GLC 300 4MATIC on the freeway under normal conditions. Without any warning lights, error messages, or prior signs of mechanical issues, the vehicle suddenly and completely lost power. The accelerator pedal became unresponsive and felt locked, and the vehicle came to an abrupt stop in the middle of an active freeway, in the second lane from the left. I had no ability to control or prevent the stoppage. This unexpected power loss directly led to a rear-end collision. The vehicle behind me sustained severe front-end damage, including airbag deployment. My passenger and I were in shock and suffered whiplash and physical injuries, with pain and bruising following the impact. I suspect the most likely causes may be an Electronic Throttle Control failure or a false activation of an Active Safety System. I opened a case with MBUSA (Case #16298894) immediately after the incident, but I have not received any updates on the investigation. This was a dangerous and life-threatening failure, and I am deeply concerned that it could occur again to other drivers if not addressed.

While driving on the highway I began to hear an unusual amount of wind noise inside the car. I thought the sound was coming from the sunroof, though it was completely closed. I pushed the button to confirm it was sealed, but the noise continued. Shortly after, I heard a loud cracking sound followed by a sudden pop. I looked in my rearview and saw something flying but didn’t immediately recognize what it was. I pulled over to inspect the situation and discovered that the entire exterior trim panel between the windshield and sunroof had detached. Another driver, who had been behind me, also pulled over after being struck by the debris. Thankfully, there were no bodily injuries, but this incident could have resulted in a serious accident. A large, fast-moving piece of trim flying off a vehicle at highway speeds presents a significant danger to other drivers, especially if they try to swerve to avoid it. I took my car to a Mercedes-Benz dealership for inspection and potential repair. I informed the service advisor that I had seen documentation of a recall involving the same issue, detachment of the sunroof panel on vehicles of the same make, model, and year as mine. However, I was told that my vehicle was not eligible for the recall based solely on its VIN and that Mercedes would not cover the cost of repairs. This is not a typical wear-and-tear issue. Structural components of a car should not randomly detach, especially on a vehicle that is only 5 years old and has been properly maintained. It is extremely concerning and, in my opinion, negligent for Mercedes-Benz to be aware of this defect and yet fail to extend the recall to all affected. The advisor acknowledged this issue was likely due to a problem with the adhesive used to secure the panel, something he said he had seen happen on other vehicles. Despite this, I was told I would be fully responsible for the repair costs. There were no warnings or signs this would this happen, the panel detached suddenly.

With approximately 57,500 miles, the car began idling roughly, misfiring and losing power. The dealership has diagnosed it with a cracked cylinder head which will require a replacement at a cost of $9,765.00. The dealership indicated this is a common issue with the M264 engine (rear wheel driver) in the GLC300 and the M260 engine (the front wheel drive version) has already had a service extension for 15 years/180,000 miles. This type of failure should not occur at this mileage or even significantly more.

For the past 6 months, the monitor in my SUV wont come on when I turn on the truck. Even when I turn the vehicle off, remove the key and step out of the vehicle, it will still do it until like the I next day. Often, still, when I am putting my car in reverse, the camera does not work. Very often. This put the safety of me and my children at risk as this is not what I am accustomed to as far as safety is concerned. I took the car to Mercedes Benz dealership here in Augusta GA and showed multiple videos of the screen not coming on or not working when I had it in reverse, they were to charge me $6000 to get this fixed at no fault of my own. There were not prior warnings. But what was odd was when I typed in my VIN number into the Mercedes Benz website, the recalled appear. When I called Mercedes Benz, it was stated that my vehicle was not apart of the recall with the same exact problem.

Panoramic sunroof blew off vehicle while driving. Other drivers were put at a risk from a vehicle component flying through the air at high speed. The vehicle has been inspected by the dealership. No warnings prior to the problem. There is a recall with Mercedes Benz for this issue buy my VIN is not the included number but should be included.

•Jan 2025, while the car owner was driving her GLC300, a warning light came on, the car shook and then shut down. AAA tow truck suggested Green’s Garage as an approved nearby repair shop. Car was towed there and repaired for approximately $450.00. •[XXX], late afternoon, the same problem arose but the car did not shut down. The car owner drove the car home and the car was dropped off at Green's Garage (GG) on the morning of May 27. Late that afternoon, GG called us to tell us the problem is not related to the January repair…Even though the symptoms were exactly the same as January with the exception of the car not shutting down. GG later stated the new problem is related to the spark plugs and that the cost to repair would be about $450.00. We agreed. •The next day (Wednesday) late in the afternoon GG called us to tell us that they found an additional problem. One of the fuel injectors was leaking. To fix the fuel injector plus the spark plugs would cost about $1,300.00. We agreed. •The car owner picked up the car late Thursday afternoon. Nothing was fixed, the engine warning light immediately came back on and the engine shook, so we have formally disputed the $1,300.00 credit card charge with our bank. [XXX] took the car on June 4 at 9:00 AM to Mercedes of Coral Gables for a pre-arranged $360.00 diagnosis. On June 5 we were informed that the engine and transmission mounts collapsed for a repair charge of $2,518.00. Also, the cylinder head valve seats are leaking and need replacing for a charge of $11,757.00. Total $14,275.00. Mercedes Benz should pay for this. Our car is a 2020 model with only 63,000 miles, but the problems started at less than 60,000 miles. We have read that this problem with this engine has existed since 2024 or earlier and that Mercedes Benz refuses to acknowledge the situation or pay for the repairs. It is dangerous to drive this car. Mercedes should be held responsible for all repairs and and accidents caused by this malfunction. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION