2020 Mercedes-Benz GLC 300 engine problems

Filed Oct 26, 2026 · Electrical, Engine · MD

On October 23, 2026, my 2020 Mercedes-Benz GLC 300 unexpectedly lost engine power while I was in traffic, without advance warning. When I attempted to restart it, the engine started, shook, and shut off again. A 12-volt battery warning appeared during the incident. On October 26, a dealership representative told me a software issue caused the shutdown and that a software update was needed. They said the update would be performed at no charge, although I would owe a diagnostic fee. I am concerned that the vehicle could lose power without warning again, especially at highway speeds. I am requesting that the federal safety agency review this incident for a possible safety defect.

Filed Aug 31, 2026 · Engine · NH

My check-engine light recently illuminated, and diagnostic testing identified fault code P06DA00, relating to the oil pump control valve circuit. I have been quoted over $5,000 to replace the oil control valve and oil pump harness. I was quoted the following by Mercedes Servuce in Manchester, NH- Oil Pressure Regulator Valve: need to remove lower oil pan only to access oil control valve and replace the valve and sub harness. $5013.52. This is a known issue. My vehicle has been well maintained, and I have been advised that it is otherwise in excellent mechanical condition. I intend to keep and drive this vehicle for many more years, which makes it particularly disappointing to encounter a repair of this magnitude for a component that is not considered a routine maintenance or wear item.

Filed Jun 25, 2026 · Engine, Transmission · CA

My 2020 Mercedes-Benz GLC 300 triggered check engine light with code P06DA (engine oil pressure control) at 40,000 miles. The failed component is an oil pressure control sensor/solenoid worth approximately $200. However, due to Mercedes-Benz's engine design (M264 engine), the entire engine must be removed from the vehicle to access and replace this part. Repair estimate from authorized Mercedes-Benz dealership (Mercedes-Benz of Stevens Creek): $8,391. SAFETY CONCERN: Loss of oil pressure can cause catastrophic engine failure while driving. Engine seizure at highway speeds poses serious risk of loss of vehicle control, potential accident, and harm to occupants and other drivers. This is a known, widespread design defect affecting Mercedes-Benz vehicles equipped with M264/M274 engines across multiple model lines: GLC 300 (2019-2023) C 300 (2019-2023) E 300 (2019-2023) GLC 43 AMG, C 43 AMG GLB 250, A 220, CLA 250 Mercedes-Benz's own authorized dealership confirmed they are "seeing this issue more and more." Despite awareness of this widespread defect, Mercedes-Benz has not issued a recall or Technical Service Bulletin. The design makes repair financially prohibitive ($8,000+), meaning many owners continue driving with compromised oil pressure — creating an ongoing safety hazard on public roads. Mercedes-Benz refused to repair under goodwill, then denied repurchase after 30-day review. They have left consumers with no remedy for a known safety-related design defect. I am requesting the federal safety agency investigate this as a safety defect affecting potentially hundreds of thousands of vehicles.

Filed May 13, 2026 · Engine, Fuel system · NJ

I have had my car for almost two years. This problem has been on-going the whole time. It happens intermittently, I never know. I will be driving it and usually when I am making a turn or pulling onto a main road, you press the gas to go and the car hesitates and makes a loud brooooooooom sound like it is trying to go or figure out what to do and if you are pulling out onto a main road with on comming traffic, this is dangerous. We have seen information that on the 2019 and 2018 GLC300's this has been documented, my car is a 2020 but it's the same thing. It's like the car hesitates and slows down when it should go!

Filed Jan 22, 2026 · Engine · SC

Premature oil pump failure on a 2020 Mercedes-Benz GLC 300 with 71,000 miles. The check engine light illuminated on December 29th, 2025 and with no other warning symptoms. The vehicle has been maintained properly, including regular visits to Mercedes-Benz dealerships. The oil pump is a critical engine component that should not fail at this mileage. It has been recommended to not drive the vehicle without repairing as oil can leak onto a hot engine. This issue has been confirmed by a Mercedes dealer. Mercedes-Benz has offered $1,000 in goodwill on a $7,400 repair, which is unreasonably low given the nature of the failure. The dealer is advocating for higher goodwill, but corporate has refused to escalate or provide a breakdown of the offer. This failure appears to be a premature mechanical defect rather than normal wear, and I am filing this complaint to request federal tracking and review.

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 Oct 30, 2025 · Engine, Fuel system · OK

Nationwide known cylinder head issues. Cylinder head work needing replaced.

Filed Oct 20, 2025 · Engine · NJ

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.

Filed Oct 10, 2025 · Acceleration, Engine · TX

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)