What 61 owners told NHTSA about the 2021 Mercedes-benz GLC Coupe

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.

NHTSA ODI 11739133

Getting P06DA trouble code meaning that there is something wrong with the oil pressure solenoid in the oil sump. this is a known issue where the wiring of the solenoid get frayed. cost of repair for the (cheap part) is $7,500 because of 18 hour labor involved. MB knows this is an issue with the wiring in the solenoid. I'm not sure if there is a fire risk because of the frayed wires.

NHTSA ODI 11735862

This is a well-known issue with these engines. See TSB (Service Bulletin) The 2021 Mercedes-Benz GLC 300 has 42,000 miles and the warranty ran out 2 weeks ago. The vehicle is up-to-date on service. Fault code P06DA00 Engine Oil Pressure Control Circuit/Open. The Yellow Check Engine Light came on and the engine does not run properly and causes engine damage. We had to drive it slowly, under 45 mph, to the nearest dealership. This is a safety issue. To replace the oil pump control valve solenoid and the wire harness for this feature is $5009.00 at Mercedes-Benz. The part cost is about $300 retail, and the rest is all labor fees.

NHTSA ODI 11718651

Cylinder head valve seat leak ..vehicle Mia fires and check engine light on

NHTSA ODI 11709578

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.

NHTSA ODI 11709709

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. 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.

NHTSA ODI 11707845

There is a hesitation in or "shuddering" that causes the car to go into limp mode while in operation. I was in traffic and the car just powered down and would not get up to and or maintain speed. I contacted the local dealership and was told that there are other models and or engines in this car that have this issue and that they actually have a recall on this issue. The dealership noted that they have 1 or more that require this exact repair on every single week. The dealer told me what was wrong with it by the code it threw... He didn't have any hesitation because he is so familiar with this issue. The warning lights came on after the car powered decreased... there was no "pre" warning that this was going to happen.

NHTSA ODI 11698959

Twice my car slowed down tremendously in traffic because of a bad cylinder head. I drive a 2021 Mercedes GLC 300 4matic with 33,529 miles. In reviewing other complaints, this is a common and known complaint. My check engine light came on and I could not go over 40 mph. This is very dangerous.

NHTSA ODI 11696080

Car has experienced rough idling, sluggish to no acceleration, check engine light illuminates and no shifting of gears regardless of speed. It appears to be going into limp mode. This has occurred monthly for the last four months. After pulling over, the car is turned off, wait five seconds and then turn it back on the car operates like nothing has happened. Here is when it has happened: 1.In a drive-thru lane to get some food 2.Waiting in a left-hand turn land 3.Driving through a parking lot at 10 mph 4.Driving on a road at 45 mph The date below is the last occurrence.

NHTSA ODI 11695359

Check engine light came on. Code was P219D mixture formation is irregular on cylinder 2. Informed today, the cylinder will need to be replaced entirely for about $10,000. Concerned that although this did not happen to me, others have stated the vehicle completely stalls while driving.

NHTSA ODI 11688954

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)

NHTSA ODI 11683317

Head problems

NHTSA ODI 11667209

In September 2024 my vehicle's engine light came off and the car was struggling to accelerate, especially in highway. I took it to Mercedes Benz of Cincinnati and they acknowledged the fault, made some repairs (under warranty) but the mechanic told us he had already seen quite a few of these cars needing the engine to be replaced. The problem keep coming back and took in in May 2025 (4 months after warranty expired) with the same exact issue. Now they said it is a cylinder head that needs replacement and that it will cost me $10K. This problem has now been reported by several drivers for this model car within less than 5 years of being made. In Canada, the same type of engine has seen same problem so Mercedes extended the warranty for 15 years on the cylinder heads. They need to do the same for the GLC engines and cover our repairs.

NHTSA ODI 11661749

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.

NHTSA ODI 11660968

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)

NHTSA ODI 11649913

While driving my vehicle on March 3, 2025 the check engine light came on. Additionally my vehicle began to shake. I was scheduled for a service appointment on March 5, 2025 and told the service department the check engine light need to be addressed. Upon inspection, it was determine the cylinder head needed to be replaced due to a leaking exhaust valve. Estimated cost of $8,818.12. I was devastated and disappointed we had a 2020 Mercedes GLC 300 had the EXACT SAME PROBLEM in 2023. The cost to repair was estimated at $9000!!! How coincidental is that 2 vehicles in the same family have the same problem on newer model vehicles!!!! After researching the web, we discovered that the warranty was extended on the M260 cylinder head however my engine is M264 engine just for RWD cars. Mercedes will not cover it even though this is the 2nd GLC 300 that WE have reported the problem with the cylinder head. They would not even replace the part and we pay for the labor. I am truly disappointed and most likely never be a Mercedes purchaser again. Especially since they cannot stand behind their product. The cylinder head failed and caused my daughter to be placed in harm's way by beginning shaking while driving. This could have caused an accident and put others at risk. This problem has been confirmed by 3 different dealerships on 2 different vehicles( 2020 and 2021 Mercedes GLC 300). It has been inspected by the dealership that confirms it is leaking and needs to be replaced and confirmd it was not the negligence of the driver. There were no warning signs besides the check engine light coming on.

NHTSA ODI 11648292

High beam can't auto dim Fuel pump fail to operate, misfires, and shut down while driving

NHTSA ODI 11646060

While drive check engine light came on and car would go past 20 miles per hour. This is the second occurrence. First time this occurred October 2023 and covered under warranty. Head Gasket blew.

NHTSA ODI 11622148

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

NHTSA ODI 11620459

Vehicle has a known engine failure. Leaking valve in Cylinder head. Cylinder 3 injector is faulty

NHTSA ODI 11618196

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.

NHTSA ODI 11607115

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!

NHTSA ODI 11565159

This is the 3rd incidence of this issue (July, Oct, Dec), but we have been advised that a software update is not yet available from the manufacturer. In all instances, we were travelling at a normal rate of in-city traffic (30-45 mph) and all of sudden the vehicle will not accelerate above 25 mph regardless of the position of the throttle. My dealer, Mercedes Benz of Tampa, advises that the problem can only be corrected permanently with a "software update" which is not yet available. This is a major safety issue, especially on the highway, as the vehicle could suddenly and unexpectedly be unable to accelerate, in fact, decelerates at random times without warning.

NHTSA ODI 11559715

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.

NHTSA ODI 11543826

The contact owns a 2021 Mercedes-Benz GLC300. The contact stated that while his wife was driving at an undisclosed speed, the "Add 1 quart of oil" message was illuminated. The contact's wife did not pull over and continued driving while the "Stop driving" warning message was illuminated. The contact's wife was able to drive to the residence. The contact noticed there was a quart of oil on the floor from the engine compartment and detected a burning oil odor. The vehicle was towed to the dealer and the dealer replaced the O-ring. The vehicle was repaired but remained at the dealer. The manufacturer was not made aware of the failure. The failure mileage was unavailable.

NHTSA ODI 11434738