Mercedes-Benz GLC 300 engine failure problems

Filed Aug 8, 2026 · Engine, Fuel system · NY

My 2022 Mercedes-Benz GLC 300 (17,700 total miles) suffered a catastrophic structural engine block failure and an explosive loss of propulsion while driving at highway speeds. This occurred exactly 6 days and 183 miles after a franchised Mercedes-Benz dealership performed the official fuel pump impeller safety recall (the federal safety agency Campaign 23V‑445).The dealership's official repair invoice documents that the technician custom-modified the recall remedy by reusing parts, explicitly stating: 'Relocated floater from old pump onto new fuel pump.' Simultaneously with the mechanical engine failure, a 'Reduce Engine Oil Level' message flashed on the dashboard, indicating severe fuel dilution from the compromised fuel system.The dealership is actively violating federal recall mandates by refusing to investigate this failed safety remedy unless I sign an open-ended financial check for a diagnostic and teardown fee. They have also revoked my substitute transportation to coerce payment. Mercedes-Benz USA Corporate Case Number 23652724 has been opened. I am requesting a federal safety investigation into this dealer's non-compliant recall remedy execution."

Filed Jul 3, 2026 · Brakes, Electrical · IN

While driving down a busy neighborhood street 2 lanes with cars on both sides making it a 1 lane road pulled over to the side a little to let cars pass. All of a sudden ALL electrical and engine stopped and turned off. Only thing that was powered was instrument cluster with multiple warnings like SRS Malfunction, Steering Malfunction, SOS Inoperative, Parking Brake and more. We believe the car had also shifted to park on its own. No power to anything not even hazard lights. Nothing electrical had any sort of power. Could not even turn car off completely could not get the instrument cluster to turn off with ignition button. When I say everything electrical had no power I mean everything except instrument cluster. Hazard lights power locks, lights of any kind, ignition switch, gear selector, windows, sos feature, nothing had power. I could not imagine having this issue driving on the interstate and having the car completely loose ALL electrical power and what could happen to specially with a SRS malfunction and issue with steering. Had to have a wrecker come with wheel dollys because car could not be put in neutral and towed to Mercedes dealer. Upon their inspection they found the Circuit 30T relay to be stuck in the open position which killed power to everything so the technician replaced the engine compartment pre-fuse panel. It is such a unsafe and very hazardous issue to have a relay failure to where all power is lost especially if you were driving on interstate especially at night with traffic to loose everything electrical even hazard lights and headlights, SRS maltunction, Steering. Mercedes needs to figure this very unsafe issue out.

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 Jun 3, 2026 · Engine, Transmission · CA

Component Failure: The vehicle is equipped with the M274 2.0L turbocharged engine, which suffered a major internal mechanical defect. An authorized Mercedes-Benz dealership diagnosed the vehicle at 79,504 miles with a malfunction in the crankcase ventilation system alongside severe internal defects, quoting a total repair estimate of $9,851 to perform extensive engine work. Safety Risk: This known manufacturing defect involves premature failure and cracking of the pistons, which poses an immediate safety hazard due to potential catastrophic engine failure and sudden, complete loss of motor power while driving at highway speeds. The manufacturer has failed to offer an extended warranty or recall for this known issue on the 2018 model year.

Filed May 7, 2026 · Electrical, Transmission · NY

On April 16, 2026, within minutes of being released from a certified dealership, my 2019 Mercedes-Benz GLC 300 suffered a sudden and total loss of propulsion while traveling at high speed on the Belt Parkway (NY). Despite depressing the accelerator, the vehicle failed to maintain speed and stalled in active traffic. This created an immediate life-safety hazard, forcing me to navigate across multiple lanes without engine power to avoid a high-speed rear-end collision. The vehicle was released to me by Mercedes-Benz of Brooklyn on April 16, 2026, following a repair for which I paid $2,134.94. The dealership diagnosed the issue as a wiring harness/sensor fault and formally certified the vehicle as "Found OK" and safe for operation. The catastrophic failure occurred only 22 minutes after I departed the dealership lot. The vehicle had to be towed back to the facility immediately. Upon the vehicle being towed back on April 16, the dealership admitted via recorded voicemail that the initial $2,134.94 repair was a misdiagnosis. They subsequently issued a new diagnosis for a "Valve Body" failure and a new quote of $6,424. The dealership's Service Director has since admitted the vehicle suffers from concurrent transmission and engine failures, rendering the car a liability. This represents a critical failure of the powertrain and electronic control systems. Releasing a vehicle that suffers a total power loss on a highway immediately after a "certified" repair is gross negligence. I am reporting this to the federal safety agency as a catastrophic failure of a safety-critical component (Transmission/Valve Body) that resulted in a "dead-stick" situation on a major New York thoroughfare, posing a severe risk to myself and other motorists. The vehicle remains at the dealership. Mercedes-Benz USA has offered only a $2,000 "goodwill credit," which does not address the safety defects or the initial misdiagnosis. No recall has been initiated for this batch.

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 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 Aug 25, 2025 · Transmission · 51,519 miles · OR

The contact owns a 2022 Mercedes-Benz GLC300. The contact stated that while driving 60 MPH, the accelerator pedal was depressed; however, the vehicle failed to accelerate as intended. The contact stated that there were several unknown warning lights illuminated before the engine seized. The vehicle was restarted; however, while driving at an undisclosed speed, the failure reoccurred. The contact started the vehicle again, and the vehicle was slowly driven to the residence. The vehicle was not diagnosed or repaired by an independent mechanic or the dealer. The manufacturer was not made aware of the failure. The failure mileage was approximately 51,519.

Filed Aug 3, 2025 · Engine, Transmission · CA

Defect Summary: Since 2024, my 2022 Mercedes-Benz GLC300 has had a persistent, abnormal engine noise consistent with the sound of a 4-cylinder diesel engine, despite being gasoline-powered. The noise occurs both while idling and in motion. On several occasions, the coolant warning light illuminated while the noise persisted. The defect has worsened over time, becoming louder and more frequent. Events & Safety Risks: The dealership repeatedly claimed “no problem found” because no warning lights appeared and no scanner codes were present, ignoring my time-stamped video evidence. At one point, I was advised to drive the vehicle from Morgan Hill, CA to the dealership while making the loud noise for diagnostics — an unsafe recommendation. When the coolant warning light appeared, the service department planned only to top off coolant. I insisted on a diagnostic, which revealed a coolant hose leak. Driving with a leak could cause overheating and sudden engine failure, creating a serious safety hazard for myself, my child, and other motorists. Repair History: Multiple visits to Mercedes-Benz of San Jose (2024–2025) for the same defect. Each time, the defect was dismissed or not resolved. No meaningful repairs were performed. The issue persists today. Evidence: Time-stamped video proof of defect, full service records, and documentation of correspondence with the dealership are available. Safety Concern: This unresolved defect creates a risk of sudden engine failure or overheating while driving, potentially causing loss of control or stranding occupants in unsafe conditions.