Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2021 Mercedes-Benz GLC300 owners, lightly cleaned up (personal details are redacted by NHTSA).
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 contact owns a 2021 Mercedes Benz GLC300. The contact stated that while driving at a low speed, the vehicle began to shake as the check engine light appeared on the instrument. In addition, the contact stated that the vehicle began to hesitate upon the depression of the accelerator pedal. Due to the failure, the vehicle was towed to a dealer where the vehicle remained in the dealer's possession for weeks. The contact was later informed that the engine cylinder cap was defective and needed to be replaced. The vehicle was then towed to an independent mechanic where it remained in their possession and had yet to be repaired. The manufacturer was notified of the failure and referred the contact to the NHTSA Hotline to file a complaint. The failure mileage was approximately 56,600
The contact owns a 2021 Mercedes Benz GLC300. The contact stated while driving approximately 65 MPH, the vehicle lost motive power and failed to accelerate properly while depressing the accelerator pedal. The contact pulled over to the side of the road and turned off the vehicle. After restarting the vehicle, the vehicle operated normally. The cause of the failure was not determined. The local dealer and manufacturer were contacted and informed the contact that the VIN was not included in NHTSA Campaign Number: 23V445000 (Fuel System, Gasoline). The contact stated that the vehicle had experienced the failure listed in the recall. The failure mileage was 28,000.
The contact owns a 2021 Mercedes-Benz GLC300. The contact stated while driving at various speeds, the vehicle hesitated to accelerate while the accelerator pedal was depressed. The contact stated there was no warning light illuminated. The vehicle was taken to a local dealer but was not diagnosed or repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 7,000.
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. …
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. …
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 NHTSA 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. …
On [redacted] 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.
The vehicle is experiencing an intermittent, sudden, and life-threatening drop into "limp home mode" while driving, creating an severe speed differential with surrounding traffic.First Incident (50,584 miles): The vehicle entered limp mode. Authorized Mercedes service center scanned the car, confirming Fault Code P019185 (Rail pressure sensor malfunction / signal above permissible limit value). The dealer applied an Engine Control Module software patch under Mercedes TSB LI07.70-P-078047.Second Incident (53,695 miles): Less than 3,000 miles later, the exact same sudden powertrain failure recurred. …
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.
Engine complaints in other GLC300 years
Frequently asked questions
How common are engine problems on the 2021 Mercedes-Benz GLC300?
NHTSA has 30 complaints about the engine & cooling of the 2021 Mercedes-Benz GLC300, 45% of the model year's 67 complaints.
Is there a recall for 2021 Mercedes-Benz GLC300 engine problems?
No. NHTSA lists no engine & cooling recall for the 2021 Mercedes-Benz GLC300, though it has 9 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2021 Mercedes-Benz GLC300 engine problems start?
Half of the complaints with a recorded mileage happened before about 7,000 miles, and 57% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 0 fires and 0 injuries to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.