Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2017 Mercedes-Benz GLC300 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2017 Mercedes-Benz GLC300. The contact stated while driving at an undisclosed speed, the accelerator pedal was depressed, however, the vehicle failed to accelerate as intended. In addition, the check engine warning light illuminated. The vehicle was taken to the dealer where it was diagnosed with a failed positive crank valve. The contact was informed that the positive crank valve needed to be replaced. In addition, the contact was informed that the repair was covered under an extended warranty program, however, the parts were on backorder. The vehicle was not repaired. The contact stated that the failure began in December 2023, however the warranty repair was completed in September 2024, due to parts being on back order. The vehicle was repaired, however, the failure reoccurred. …
The contact owns a 2017 Mercedes-Benz GLC300. The contact stated while driving at an undisclosed speed, the check engine warning light illuminated. The vehicle was taken back to the dealer and the contact was informed that the vehicle was repaired. The contact stated that the dealer had only reset the codes. In addition, the contact stated that the tire pressure sensor warning light was illuminated. The contact stated that the sunroof latch failed to close as needed using the sunroof power switch. 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 88,100.
The contact owns a 2017 Mercedes-Benz GLC300. The contact stated that while at a stop light, the vehicle independently shifted to neutral(N) for approximately 5 minutes. The vehicle failed to release from neutral when the driver shifted the gear shifter. The contact stated that the transmission then released from neutral(N), and the vehicle jolted forward. The check engine warning light was illuminated. The vehicle was taken to an independent mechanic, who was unable to determine the cause of the failure. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not contacted. The failure mileage was approximately 75,000.
The contact owns a 2017 Mercedes-Benz GLC300. The contact stated that while driving approximately 55 MPH, she detected white smoke coming from the tailpipes. There were no warning lights illuminated. The contact was able to pull over. The vehicle was towed to the local dealer who placed a camera inside the engine and noticed that the piston had fractured and detached inside the engine. The contact was informed that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was contacted but no additional assistance was provided. The approximate failure mileage was 88,000.
What component or system failed or malfunctioned, and is it available for inspection upon request? Car is at Mercedes dealer for repair. How was your safety or the safety of others put at risk? Yes, car lost acceleration on freeway and put other drivers at risk on the road. Lucky to get off freeway and pull over without any injuries. Has the problem been reproduced or confirmed by a dealer or independent service center? Dealer provided feedback cracked piston, cylinder # 2. Reading on forums, others continue to have the same issue. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? Inspected by Mercedes bens manufacturer. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? in retrospect, some slow acceleration delays 1-2 days prior, but not consistent.
The Positive Crankcase Ventillation harness fails and check engine light goes on. Through my research I found that many C class and GLC class with same engine have had similar issues and there was a recall and covered. My particular VIN was not included in the recall but had this check engine warning sign before 50K miles warranty expires. The light always went away but now it has come back on for the third time and not going away. The cost to replace this simple module is mostly labor at 8 hours is around $2,000. I believe this is an emission component and need to be covered under state and federal emission standards warranty. The initial recall with this issue should be involved with same engine and cover all cars and SUV's with same engine. I do believe this is an Emission control device that is regulated by state and federal standards and should be covered under warranty.
I was suggest by dealer to replace crank case vent value as its blocked and quoted $300 for part and 1800 for labor cost as they need to remove whole engine and replace part. Issue is how can mercedes benz design such engine with 6-7 hrs of labor intensive work and 6 times higher labor cost than part cost. I was told this work is necessary for engine efficiency and to pass SMOG test. I feel design issue is related to car / passenger safety and environment hazard. Also it looks like a very common recurring issue with mercedes models based google search. Added to it local dealer didnt find a problem when my car is under warranty or within service packages. Warranty completed and came up with these problems.
Odometer reading more miles then driven (may have been tampered with altered) There is an electrical issue The computer required to be reprogrammed has not been done yet While driving the vehicle completely stop accelerating in the middle of traffic on the interstate placed my life in danger especially because traffic was moving rapidly the vehicle was jerking horribly also several codes came on when the service light came on also needed a pcp vale hose system they never repaired it i asked to have it repaired they agreed and then stated the vehicle had to many issues was sending to auction but yet reselling the vehicle still have not repaired completely this could be dangerous
After noticing my engine light come on, I had my vehicle checked out, the dealer informed (after spending $250.00) that the problem is the crankcase ventilation and it's a common problem. It seems the oh so familiar crankcase ventilation system is not working. This is a common problem with the GLC300 and Mercedes Benz needs to correct it. The engine is not being ventilated properly and the overwhelming smell of gasoline engulfs the interior of the vehicle. This is putting mine and the life of my family at risk, due to a faulty manufacturer issue. Mecedes Benz needs to obviously correct the faulty parts they use as soon as possible, before someone loses their life.
There are lots of 2017 GLC 300 that has been having issues with PCV system that are malfunctioning that could cause engine failure. Customers are forced to spend $2000 plus to have this fixed rather than Mercedes owning its problem and fixing it. For your reference please check glcforum.com where glc owners are ranting their issues with PCV systems. https://www.glcforums.com/threads/2019-glc300-4matic-pcv-code-crankcase-ventilation-oil-separator.7997/
Engine complaints in other GLC300 years
Frequently asked questions
How common are engine problems on the 2017 Mercedes-Benz GLC300?
NHTSA has 37 complaints about the engine & cooling of the 2017 Mercedes-Benz GLC300, 37% of the model year's 99 complaints. The component named most often is exhaust system (1 mentions).
Is there a recall for 2017 Mercedes-Benz GLC300 engine problems?
No. NHTSA lists no engine & cooling recall for the 2017 Mercedes-Benz GLC300, though it has 12 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 2017 Mercedes-Benz GLC300 engine problems start?
Half of the complaints with a recorded mileage happened before about 60,000 miles, and 44% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 2 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.