2020 Mercedes-Benz GLC 300: engine stalls while driving

Filed Dec 8, 2025 · Engine · CT

The engine in my 2020 Mercedes-Benz GLC 300 suddenly malfunctioned while driving on two separate occasions. The vehicle began shaking violently and lost power without warning. I could not accelerate and had to pull over immediately. I turned the vehicle off and restarted it to regain limited driveability. On the second incident, the power loss was so abrupt that it felt as if I had been rear-ended. I feared the vehicle would stall in traffic and cause a crash. Following these events, the check engine light remains constantly on. The dealer inspected the vehicle and confirmed excessive valve leakage into the exhaust system, requiring a complete cylinder-head replacement. They warned the failure will worsen and could result in sudden power loss again. This defect poses a serious safety risk. If the power loss occurs while merging or at highway speeds, it could easily lead to a rear-end collision. The vehicle has relatively low mileage for such a severe internal engine failure, and I have learned that other owners of this same engine have reported similar issues. Sudden stalling or loss of acceleration places occupants and other drivers in danger. There were no warning messages prior to the failure, and the problem has recurred. The vehicle is available for inspection, and the defect has been confirmed by a Mercedes-Benz service center. This appears to be a mechanical defect in the engine design, potentially involving valve seat failure. An investigation is needed to determine if this issue is widespread and whether a recall or manufacturer action is required to prevent accidents or injuries.

Filed Dec 3, 2025 · Engine · GA

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.

Filed Apr 28, 2025 · Engine · MS

Some M264 Engines are predisposition to premature cylinder head failure, this issue can cause significant misfire issues. It also leads to a costly repair. We experienced issues with a P219D code , we had the coils and plugs replaced on a 2020 GLC 300 with 38.5 k miles. We assumed that this issues with a misfire and check engine light were corrected. My wife was turning onto [XXX] in Pascagoula MS last week, the car misfired and stalled with cars and semi trucks rapidly approaching, several cars had to slam on breaks and this issues almost caused a significant wreck. She had to pull over to gain her composure, the car would not over above 2k RPMs. I showed up and was able to to restart the car , I immediately drove it back to the repair shop. The shop bore scoped the #2 cylinder, the valve seating is significantly damaged, thus causing a significant loss of engine power / misfire in cylinder 2. I reached out to Mercedes Benz USA and was advised to take the GLC300 to the dealer that sold us the car. At present the is being evaluated by the MB dealer. MB USA is well aware of issues regarding cylinder head failure. There is actually a low mileage GLC 300 at MB of Mobile with the same problem as our MB. They have sent out service bulletins to every MB Dealership in the US regarding this issue. Likewise they have extended the warranty on several MB models that share the same engine that are mounted for front wheel drive cars, M260 engine. The M264 is an identical engine that is mounted for rear wheel dive vehicles. It is beyond obvious that a significant loss of engine power poses a threat to the driver/occupants and other vehicles/occupants on the road. MB USA is well aware of this issue with their engines. Not only do they have a service bulletin regarding this matter , they have repair protocols which include a cylinder head replacement. This is a consumer and safety issue that needs to be corrected on applicable GLC 300 models. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMAT

Filed Mar 27, 2025 · Fuel system · CA

Dear Sirs: I own a 2020 GLC300W Mercedes SUV. As of this date, It has stalled 5 times while driving on the highway and on the roads within an 8 month period. Throughout this period, I have taken the vehicle to the Mercedes dealership in Riverside, CA three times to have this inspected. After their first inspection, the dealership claimed that the problem was due to a recall on a computer software update needed. However, the vehicle stalled two more times while driving on the highway. After the second inspection, the dealership claimed the problem was due to a bad throttle actuator and charged me $2000 for the repair. Two months later, the vehicle stalled on the road once again. Currently, the dealership is inspecting the vehicle for a THIRD time. I have viewed your NHTS website and came across the federal safety agency campaign number: 23V445, Problem Description: Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2021-2023 C-Class, E-Class, S-Class, CLS, SL, GT, GLC, GLE, GLS, and G-Class vehicles. Please refer to MBUSA's recall report for specific vehicle details. The fuel pump may shutdown, which can result in a loss of drive power." I believe this is the cause of my 2020 Mercedes doing the exact same thing, however the 2020 model is not listed in this recall. Please investigate this as this may be fuel pump issue applies to 2020 models.

Filed Apr 24, 2022 · Transmission · TX

It took a few minutes to be able to completely turn left out of a shopping center while waiting in line. When finally able to turn left, the car stalled into what appeared to be neutral where I had no control to increase speed and was turning very slowly. Oncoming traffic from both ways were coming and luckily stopped on-time. I had to turn off the entire car and restart in the middle of the road in order to be able to drive again. There could've been a massive collision if cars were not paying attention on both sides. Note that the car was NOT in neutral at the time and was in drive the entire time. This same incident also happened over a year ago but thought it was something I could've done wrong or was a one-time thing. Now that it's happened twice confirms that there is something wrong with the car. The car did not indicate a power failure or warning lights during this incident. I have an appointment with Mercedes on 4/25 to get this looked at. This has been reported on other models from other car owners but we have never seen a recall. This is a serious malfunction and could've gotten myself or others killed. I do not feel safe driving this car unless it is fixed.

Filed Mar 4, 2022 · Electrical, Engine · 30,000 miles · TX

The contact's wife owns a 2020 Mercedes-Benz GLC300. The contact stated that while his wife was driving at an undisclosed speed, the vehicle stalled. The vehicle was towed to the dealer and diagnosed with ignition failure. The contact was informed that the engine needed to be replaced. The vehicle was not repaired and remained at the dealer. The manufacturer was made aware of the failure but declined to buy back the vehicle and offered a two-year service plan for a free oil change per year. The failure mileage was approximately 30,000.