2021 Mercedes-Benz GLC 300: sudden loss of power

Filed May 20, 2026 · Engine · AL

While driving in my neighborhood at 25 MPH, my Mercedes GLC300 suddenly lost power and the check engine light illuminated. My car would no longer exceed 25-30 MPH, but I drove it straight to the dealership and they said it was a faulty cylinder head and will cost $10,000 to fix! After intense negotiations, they agreed to fix it for $4,205.58, which was better, but still, that’s a lot to pay for a manufacturer’s defect! My car is a 2021 with only 67,540 miles on it.

Filed Jan 8, 2026 · Engine, Transmission · CA

Vehicle Information: Year: 2021 Make: Mercedes-Benz Model: GLC 300 Engine: M264 Mileage at time of failure: Approximately 65,000 miles Complaint Description: While driving, my 2021 Mercedes-Benz GLC 300 began experiencing repeated engine misfires and rough running, accompanied by a persistent check engine light. These symptoms began shortly after I purchased the vehicle and progressively worsened over time. The vehicle exhibited reduced engine performance and hesitation while driving. The condition was intermittent at first but became more frequent, indicating a progressive mechanical issue rather than a sudden failure. At approximately 65,000 miles, the vehicle was evaluated by an authorized Mercedes-Benz dealership and diagnosed with a catastrophic cylinder head failure, requiring full cylinder head replacement. The estimated repair cost is approximately $8,000. The vehicle has never been modified and has not undergone prior engine repairs. The failure occurred well before what would be considered normal wear for an engine component of this type. Based on the progression of symptoms, the dealer diagnosis, and similar reports from other owners of the same model and engine, this appears to be a systemic defect involving the cylinder head and valve train, rather than an isolated incident or maintenance-related issue. This condition presents a potential safety concern due to loss of engine performance, drivability issues, and the risk of reduced power while operating the vehicle.

Filed Dec 30, 2025 · Engine · NJ

While I was driving on the Garden State Parkway, my vehicle experienced a sudden loss of power and persistent misfires and my check engine light came on. I was put in a position of a significant crash risk due to the fact that the vehicle loss sudden acceleration power while entering the parkway. I was almost rear ended by another vehicle. I drove immediately to a Mercedes-Benz dealer. The dealer confirmed a catastrophic cylinder head engine failure. The vehicle had only 39,000 miles. After some investigating, there have been numerous complaints from vehicle owners with the same issue on the M264 engine (which is what my vehicle has). I request that the federal safety agency investigate the premature cylinder head engine failure. Not only was I put at risk for a possible significant accident, the manufacturer has refused to consider some reimbursement for my $10,000 repair. The vehicle was only 3,000 miles out of warranty at the time of the engine failure. A safety issue seems to be warranted and possibly a recall because of the many complaints on the GLC website. Please investigate.

Filed Nov 3, 2025 · Fuel system · FL

The vehicle lost power and will not operate over 40 mph/2000 rpms

Filed Aug 27, 2025 · Engine · WA

what happened? While driving, all of sudden, engine light was on and shaky with rough vibration consequently loss of power. I pulled over and turned off engine. Engine light disappeared after restarted. It happened again and had diagnostics at the dealership. Software update was given at first solution. However, next day, engine light on again, visited the dealership and it turned out there are leak on cylinder head. It seems a known issue. there are similar cases where vehicle could have been in critical situation. [XXX] [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed May 14, 2025 · Engine · FL

Our 2021 Mercedes is 4 years old and had the engine light come on. The vehicle has always been maintenance by Mercedes and well taken care of. The engine had a Cylinder Head Failure which resulted in a $7600 repair for a 4 year old vehicle. Mercedes refused to offer a good will repair. This is A major issue reported in 2015–2016 M274 engine which can lead to catastrophic engine failure 1. These failures often result in loss of power, strange engine noises, and in severe cases, engine seizure. The damage can extend to the cylinder head, especially if broken piston fragments impact the combustion chamber. This is a major risk for all owners of 4 cylinder Mercedes. Mercedes of Canada has already issued an extended warranty but owners of US Mercedes vehicles are left on the hook for the bill and risking their lives while this is a known issue.

Filed Mar 22, 2025 · Engine · OK

On [XXX] my GLC 300 AWD while driving back from work started shaking, went into limp mode, engine started misfiring and check engine light came on. Pulled over into a parking and called Mercedes-Benz road side assistance, they sent a tow truck and the car was towed to the Mercedes-Benz of Oklahoma City. The service department informed us of cylinder head failure and told SUV needs cylinder head replacement that would be covered under the extended Mercedes warranty. As of March 22, 2025 SUV is still at the Mercedes dealer and not fixed. This is the second time in past few months GLC went into limp mode and lost power and acceleration while on road, it was towed to the Mercedes dealer. They initially said they couldn't find anything wrong but later performed an update of engine management software on the recommendation of Mercedes-Benz USA. Car was fixed at that time. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 7, 2024 · Engine · 35,000 miles · MI · crash

The contact owns a 2021 Mercedes Benz GLC 300. The contact stated that while driving at various speeds, the vehicle would lose power and fail to accelerate upon the depression of the accelerator pedal. The check engine light would appear on the instrument panel. Despite the failure, the vehicle would resume normal operation upon restart of the engine. The vehicle was initially taken to a dealer but the dealer could not duplicate the failure. The failure worsened over time which resulted in the contact being rear-ended by another vehicle. The air bags did not deploy upon impact and the contact was not injured. A police report was filed and the contact was able to drive the vehicle away from the scene of the accident. The vehicle was taken to various dealers and independent mechanics where each diagnosed the vehicle with a defective cylinder head. The manufacturer was notified by the dealer about the failure and the manufacturer agree to cover half the cost of the repair. The vehicle had yet to be repaired. The failure mileage was approximately 35,000.

Filed Jan 12, 2024 · Engine · SC

On 12/17/2023 at approximately 6:00 am while traveling to a friends house, my car stalled out on me. The engine light came on and the car started hesitating ( sputtering) and then shut off. I tried to start the car and it did with the engine light still on. I called a tow truck and had it towed to Carlton Mercedes. On 12/18/2023 the service advisor contacted me via text to say they will do a diagnostic to find the problem and will be in touch. 5 days later, i was told that the sensors were wet due to standing rain water I encountered and that nothing else was wrong. I picked up the car later that evening. 3weeks later the same exact thing happened. The car started sputtering (hesitating) the engine light came on and it shut off. Although my VIN number was not apart of a recent recall for my make and model, I would like the Safety Department to investigate the issue and have my car added to the recall list. The recall address the issue of loss of power to vehicles of the same make and model as mine. The Mercedes Manufacture will not fix my car under the recall if it hasn't been added to the list. I don't believe the consumer should have to pay simply because the VIN was added to the list even thought the problem exist. Please Help!

Filed Sep 27, 2022 · Electrical, Fuel system · KY

My car was bought new in October 2021 & I began having problems after having it for 6 months & the mileage at that time was about 4000 miles - it was in April 2022 & the check engine light came on & I had a loss of power to where it slowed down & would not go any faster than about 30/35 miles an hour going on a straight road way & no faster than about 10 miles an hour going uphill. The engine sounded funny as well. It had to be towed to the dealership for repair. This incident happened again a month later & it was towed to the dealership at that time. The next incident just happened this month (mileage=6620) & again it was towed to the dealership for repair. Same scenarios all 3 times. This last incident, I was told that it is glitch & they don't really know what is causing my car to basically go into "limp mode"; however, they are awaiting a software update that they expect will resolve the problem, but they are not sure when it will be available for installation & did not give me a timeline. In the meantime, I was given back my car as I was the 2 other times without a resolution or security that my car is doing to make it to & from my destination. The car is still under warranty & just under a year old now. I was told by the dealership that they have no other customers complaining of this problem & they feel it is very isolated. I asked them to reach out to their corporate office in hopes of making a deal with me as I have lost all confidence in the car, but they reported having no luck in reaching anyone to discuss my problem. The 3 incidents where the car had to be towed were very scary for me as other cars were blowing their horns at me because I could not accelerate & go any faster & when I was going up a hill - it was really bad. I was very lucky that all 3 times happened not far from my home & not on the interstate as the outcome could have been very bad for me in regards to my safety.