What 5 owners told NHTSA about the 2021 Mercedes-benz AMG Glc43 4matic Coupe

The engine-driven vacuum pump and turbocharger boost-control vacuum system malfunctioned. The vehicle developed insufficient vacuum to the boost-control system, resulting in a P0299 turbocharger underboost fault and reduced engine power. The vehicle is available for inspection upon request. The vehicle experienced a noticeable loss of peak power and reduced acceleration. Although it did not enter limp mode, unexpected reduced acceleration could create a safety risk while merging onto a highway, passing another vehicle, entering or crossing traffic, or attempting to avoid a collision. An authorized Mercedes-Benz dealership scanned the vehicle, confirmed fault code P0299, and documented that vacuum supplied to the turbocharger boost-control system was too low. The dealership recommended replacing the vacuum pump and retesting the vehicle. The vehicle was inspected and diagnosed by an authorized Mercedes-Benz dealership. Mercedes-Benz USA reviewed the case and the dealership’s diagnosis as part of a goodwill-assistance request, but Mercedes-Benz USA did not physically inspect the vehicle. The vehicle has not been inspected by police or insurance representatives. The check-engine light illuminated, and the vehicle stored a P0299 turbocharger underboost fault. I also noticed reduced peak engine power and weaker acceleration. The vehicle did not enter limp mode. These symptoms first appeared at approximately 42,000 miles on or around June of 2026. Mercedes-Benz has issued an extended warranty for vacuum-pump failures on certain M157-powered vehicles that identifies the same vacuum-pump part number used in my M276-powered GLC 43 and describes similar symptoms, including low boost, a check-engine light, and P0299. Although my vehicle is not currently included in that extension, the use of the identical component and substantially similar failure raises concern that the affected population may extend beyond the listed M157 models.

NHTSA ODI 11747935

At just 30,000 miles — less than half the mileage at which these failures are typically reported — my GLC 43 was found to have active oil leaks in multiple locations: 1. Front engine covers — oil is seeping from both the front cover gasket area and migrating downward along the engine block. The dealer recommends a full reseal of the front covers at a quoted cost of $1,944. 2. Radial shaft sealing ring of the front axle gear — is actively seeping gear oil, with a quoted repair cost of $1,718. My concern is not limited to cost. Oil migrating from the front cover area toward the lower engine, accessory belt, and turbocharger assembly creates a documented fire risk. The turbocharged M276 engine operates at extremely high surface temperatures in the areas where this oil is accumulating. I will be candid: I have genuine concern about operating this vehicle until these repairs are completed, and I am troubled that a safety-relevant failure of this nature is occurring at such low mileage on a vehicle in this price class.

NHTSA ODI 11742742

2021 Mercedes GLC 43 headlight is inoperable. Same as reported in campaign 22V261000: "Headlight failure can decrease visibility for both the driver and surrounding traffic, increasing the risk of a crash." Although our car was produced before the dates reported in campaign 22V261000, I believe this is the same defect and the recall should apply to all MY 2021 cars as this is a serious safety issue. The dealer will not repair under warranty.

NHTSA ODI 11689974

Panoramic sunroof exploded while driving.

NHTSA ODI 11521032

The contact owns a 2021 Mercedes-Benz GLC43 equipped with Continental Tires, Tire Line: Sport Contact, Tire Size: 255/40/ZR21, DOT Number: AFHDD76M. The contact stated that on several occasions while driving at approximately 30 MPH and at low speeds on wet pavement, the vehicle started to shake, and a loud abnormal noise was heard in all four tires. No warning light was illuminated. The vehicle was taken to the dealer where it was diagnosed that the tires needed to be replaced; however, tires were not replaced. The manufacturer was notified of the failure and the contact was advised to call the NHTSA Hotline. The failure mileage was approximately 10,000.

NHTSA ODI 11504702