2017 Mercedes-Benz GLC 300 Problems

What owners report

Owners of the 2017 GLC 300 most often describe a check-engine light traced to the crankcase ventilation valve, usually somewhere past 45,000–60,000 miles and often quoted at $2,000 or more because of labor. A second, smaller cluster is a fuel smell or leak near the high-pressure fuel line, and a third is panoramic sunroof glass or roof-panel separation reported at highway speed and low mileage. Electrical and alert-system complaints (sunroof, wipers, seat belts, air bag warnings) tend to show up early in ownership, in some cases within the first few thousand miles.

1. 1
   Engine

   Crankcase ventilation valve failure (P052E)

   • 24 complaints (24%)
   • median 53,000 mi at 4.5 yrs old (2 state mileage, few)
   • owner-quoted repair $2,250 (median of 8 quotes)
   • filed 2021–2025

   Complaints describe the check-engine light coming on with code P052E, which dealers trace to the positive crankcase ventilation regulator valve. Several owners also report a strong fuel or gasoline smell, rough running, hesitation, or a vehicle that will not accelerate and feels like it wants to stall; a few were told the valve could eventually affect the engine or lead it to seize. Quotes reported range widely, commonly from about $1,000 to $3,000 and once much higher, with dealers citing the amount of labor to reach the part, and in several cases the part was backordered with no date given. Typically reported from roughly 46,000 to 94,000 miles, with several owners saying it appeared just before or after the 50,000-mile warranty ended.

   2 related service bulletins

   What to check: Ask for service records showing whether the crankcase ventilation valve has already been replaced, and have a pre-purchase scan done for P052E and stored engine codes. A gasoline smell in the cabin or under the hood is worth investigating before purchase.

   2 excerpts from owner complaints in NHTSA records

   “My car has P052E code with a message of Positive Crankcase Ventilation Regulator Valve Performance. My car mileage is only 13,700 as of today. I think this is a cause of a deflective part and this should be a recall item. FYI, Wen I contact a Mercedes dealership and they asked me a cost of $2,500 to fix this issue. Thank you,”

   NHTSA complaint #11491514, filed 2022-10

   “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. …”

   NHTSA complaint #11563324, filed 2024-01
2. 2
   Engine

   Engine misfire, piston damage, and loss of power

   • 12 complaints (12%)
   • median 11,000 mi at 2.0 yrs old (5 state mileage, few)
   • 2 mention a crash, fire or injury
   • filed 2017–2024

   A smaller set of complaints describe sudden loss of acceleration at highway speed, white smoke from the exhaust, or a vehicle that shuts off and will not restart. Dealers in these cases reported a cracked or fractured piston, a failed cylinder, an engine rebuild or replacement, or in one case an engine fire; a few owners say a transmission that slipped into neutral or a failed front differential was behind the loss of drive. Reported across a wide range, from under 10,000 miles up to about 88,000 miles, with several cases on the highway at speed.

   Recall 17V574000Recall 17V114000

   What to check: Have a compression or leak-down test and an engine-code scan done before purchase if there is any history of misfire, smoke, or low-power complaints, and ask whether the engine has been repaired or replaced.

   2 excerpts from owner complaints in NHTSA records

   “The engine suddenly went up in flames while driving,my wife switched off the ignition and go out of the car. There was a big hole and mercedes authorized dealer siad this is a catastrophic event. This car is new purchased on october 31st 2016 mb says they will replace the engine as it is in warranty, but sentimentally we are so upset , if the fire would have caught on to gas tank. Please suggest. …”

   NHTSA complaint #10981207, filed 2017-04, 3,000 miles

   “2017 mercedes benz GLC 300. Consumer writes in regards to engine misfire, spark plugs and cylinders. The consumer stated the engine has been rebuilt twice but, the failure persisted. The check engine light was illuminated.”

   NHTSA complaint #11419605, filed 2021-06
3. 3
   Other or unknown

   Panoramic sunroof glass shatter or roof panel detachment

   • 10 complaints (10%)
   • median 68,000 mi at 5.7 yrs old (7 state mileage, few)
   • filed 2017–2026

   Owners describe the front roof panel or sunroof glass breaking or separating suddenly: a loud bang while driving at highway speed, followed by shattered glass or trim landing in the cabin, in some cases at low outside temperatures. Others report the sunroof going off track, failing to close, or making a grinding noise when opened, and being told the rails need replacement. Some say the vehicle was not covered by the relevant recall because their VIN was not included. Reported from as little as a few thousand miles up to about 82,000 miles, including highway-speed glass breakage and sunroof track problems at higher mileage.

   Recall 17V715000Recall 23V854000Recall 21V197000

   What to check: Check whether recall 17V715000 (and any later roof-panel recall) was completed for this VIN, and open and close the sunroof through its full travel to listen for grinding or catching. Look for uneven gaps or recent sealant around the front roof panel.

   2 excerpts from owner complaints in NHTSA records

   “While driving on the I-75 north, the sunroof exploded as indicated in the picture attached. It is still unclear if the sunroof shattering was from a stray rock on the highway, or if the sunroof exploded on its own, however my concern is how the sunroof shattered and the quality of the material/glass used. What type of glass is used in this vehicle for it to shatter as it did? Is this perhaps a sign of cheaper material being used on the sunroof. There are more pics than can show more of the damage.”

   NHTSA complaint #11043584, filed 2017-11, 4,000 miles

   “While driving on the I-5 into downtown san diego we heard a loud bam, a moment later heard cracking then shattered glass from my sunroof fell into the car. There was no one directly around us.”

   NHTSA complaint #11033826, filed 2017-10, 4,900 miles
4. 4
   Air bags

   Air bag and seat belt warnings or non-deployment

   • 17 complaints (17%)
   • median 60,000 mi at 4.3 yrs old (9 state mileage, few)
   • 2 mention a crash, fire or injury
   • filed 2017–2026

   Complaints describe air bag malfunction messages, an SRS warning, air bags that did not deploy in a collision, air bags that deployed while parked, and seat belt buckles that stay latched or retractors that stick or will not extend. Some owners say the vehicle had prior safety recalls performed and still showed the same symptoms, and several report that a dealer inspected but did not repair the vehicle. Reported from low mileage (a few thousand miles) up to roughly 120,000 miles, including complaints shortly after delivery.

   Recall 18V683000Recall 18V177000Recall 17V251000Recall 17V627000

   What to check: Confirm that the rear seat belt buckle and pretensioner recalls were completed for this VIN, then check that all belts latch and release and retract fully. Have any SRS warning read before purchase, since diagnosis can be expensive.

   2 excerpts from owner complaints in NHTSA records

   “While driving vehicle, the seat belt pretensioner is activated and the seat belt light and alarm is activated. This cycle occurs throughout the drive, regardless of speed. Seems as though the seat belt latch does not sense that the seat belt is activated. This is very distracting to the driver. We reported the issue to the dealership, but have not heard anything since the report. This problem occurs on and off, randomly. May occur for a week straight, then stop for a day or two, then start again.”

   NHTSA complaint #11487340, filed 2022-09

   “The contact owns a 2017 Mercedes-Benz GLC300. The contact stated while driving at an undisclosed speed, the messages Driver’s Air Bag Malfunction - Service Required and Collision Prevention Assist Unavailable were displayed. The vehicle was taken to an independent mechanic who diagnosed and determined that the air bag had malfunctioned. The vehicle was not repaired. The contact called the dealer, but the vehicle was not inspected or repaired. …”

   NHTSA complaint #11715404, filed 2026-02, 130,000 miles
5. 5
   Fuel system

   Fuel smell or leak near the high-pressure fuel line

   • 6 complaints (6%)
   • median 62,500 mi at 6.9 yrs old (2 state mileage, few)
   • filed 2022–2026

   Owners report a strong raw fuel smell after parking or while starting, and in some cases a leak traced to the connection between the high-pressure fuel rail and the high-pressure fuel pump line. Some say an independent shop pointed to a specific recall for the leak but a dealer told them their VIN was not included. One owner also reported the fuel gauge reading empty despite a full tank, with the dealer recommending a new fuel tank. Mostly described around 55,000 to 70,000 miles, from owners who noticed the smell while parked, starting, or driving.

   What to check: After a test drive, park and smell around the vehicle and under the hood; ask a mechanic to inspect the high-pressure fuel pump and rail connections for staining or seepage. Ask the dealer to confirm whether any fuel-system campaign applies to the VIN.

   2 excerpts from owner complaints in NHTSA records

   “The fuel line leaks directly under the driver seat. Filling the cabin with fuel vapors. Mercedes has an extended warranty for this problem but only on vehicles from 2004 to 2009.”

   NHTSA complaint #11454122, filed 2022-02

   “The contact owns a 2017 Mercedes-Benz GLC300. The contact stated that she detected an abnormally strong fuel odor after parking the vehicle, and while starting the vehicle. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The manufacturer was not made aware of the failure. The failure mileage was approximately 70,000.”

   NHTSA complaint #11590367, filed 2024-05, 70,000 miles

Buying note. The 2017 GLC 300 is most worth a careful pre-purchase inspection for engine faults: scan for P052E and fuel-system codes, verify recall completion for the sunroof, seat belt, and electrical campaigns, and get service records showing whether the crankcase valve has already been replaced. Owners report these repairs can be costly mainly because of labor, so confirming work already done matters more than the mileage alone.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.