2020 MERCEDES BENZ GLC 300 Engine Problems

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.

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.

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

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.

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)

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.

•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

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

The check engine light was on. There is a problem with the oil pump valve of the engine. The problem has been confirmed by a dealer and an independent mechanic.

The check engine light illuminated, I took the car to the dealer I bought. They said the cylinder head on the engine needs to be replaced, when I check the internet it seems it is a known issue for Mercedes X253 but there is not a recall program. I bought the car from the dealer, and put on 5k miles in a year.

Car was running rough so I took it to the mercedes benz dealer they diagnosed the problem as cylinder 1 misfire and and cylinder head needed to to be replaced which I did $5500 dollars later this is a common problem and Mercedex Benz needs to recall the engine and reimburse me

The contact owns a 2020 Mercedes-Benz GLC300. The contact stated that while stopped at a red light, the vehicle started shaking and jerking. The check engine warning light was illuminated. The vehicle was taken to a dealer where it was diagnosed that the cylinder head needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 40,000.

Mileage: 40,000

The contact's son owns a 2020 Mercedes-Benz GLC300. The contact stated that when the vehicle was taken for the State Emissions Inspection, the vehicle failed the inspection due to a defective "smoke cannister". The contact stated that after the vehicle failed the inspection, the "check emissions" message appeared on the instrument panel. The contact called a dealer and was advised to purchase and install the smoke cannister. The vehicle was taken to an independent mechanic who installed a new smoke canister; however, the failure reoccurred, and the vehicle failed the State Emissions Inspection test again. The vehicle was taken back to the dealer where the vehicle was diagnosed with a defective smoke canister and valve. The vehicle was not repaired. The manufacturer was informed of the failure. The failure mileage was unknown.

Engine began unpredictably running rough. Would lose ability to accelerate, in traffic. Engine light came on. Originally took to dealership, computer indicated a “misfire cylinder 2” was told by mechanic at dealership it was possibly “bad gas” and they cleared all codes. Continued to get worse. Took vehicle to a licensed “Mercedes Doctor” mechanic who had to replace cylinder head to correct. Vehicle is now running better than new!

The contact owns a 2020 Mercedes-Benz GLC300. The contact stated that while driving at an undisclosed speed, the engine misfired. In addition, the check engine warning light was illuminated. The contact was turned off and restarted the vehicle. The contact stated that the vehicle drove as needed. The contact stated that the vehicle was taken to an independent mechanic however, the failure was unable to be duplicated. The vehicle was not repaired. The contact stated that the failure occurred intermittently for several months. The vehicle was taken back to the independent mechanic where it was diagnosed with a failed engine vent seat and the engine vent seat needed to be replaced. The vehicle was not repaired. The contact was advised to take the vehicle to the dealer. The vehicle was taken to the dealer where it was diagnosed with a failed engine vent seat and the engine vent seat needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and a case was filed. The failure mileage was approximately 25,000.

Mileage: 25,000

Engine failure needs cylinder head replaced which is very common amongst this car. Same make and model is covered under warranty but mine has a different engine that isn't covered. These cars were made during covid and have faulty parts.

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.

Mileage: 30,000