2023 Mercedes-Benz C-Class Reliability Report

Hard braking with no cause is the main complaint. The car slams on the brakes and tightens the seat belts with nothing in the way, at speeds up to 70 mph, sometimes with no alert. Turning the system off does not always stop it. One crash involves a C300 that braked hard, refused to accelerate, and was rear-ended, injuring a passenger. Another report says automatic braking gave no warning and did not act before a rear-end collision. Some owners also report brake noise that persists after rotor and pad replacement.

Stalling in traffic or at lights is the most common report. The car shuts off, shows a "malfunction" message, and restarts after a press of the start button. Persistent check engine lights appear within the first few hundred miles, and dealers often find no codes. Some owners report waiting on recall parts or stalling that continues after dealer work. Single reports describe a broken piston that required a new engine, an oil leak on a parked car, and a C300 that stalled at 3,900 miles and was told it needed a water pump.

Panoramic sunroofs, and the glass panel between them and the windshield, shatter while driving with no impact. One owner was quoted $4,000 for the repair. Power rear hatches open while the car is unattended or close with force, and one head injury is reported. Several reports describe recall repairs delayed because parts were unavailable. Others cite a low front bumper pulled loose by a parking block and window trim coming off at highway speed.

Sidewall bubbles and sudden blowouts after small potholes or bumps are the main pattern, mostly on low-profile and run-flat factory tires. Some owners replace several tires within the first year and a half, and bubbles appear on tires with under 8,000 miles. In one C300 report, a flat damaged both the sidewall and the rim. In another, the dealer blamed outside damage rather than the tire. No crashes are reported, but several blowouts end with a tow.

The car brakes hard or stops completely with nothing ahead, often with no warning light, at speeds from 25 to 45 mph. Adaptive cruise and speed limit assist also cut speed abruptly after misreading signs. Several C300 owners say recalibrating or replacing sensors did not fix it, and problems start as early as 1,000 miles. The system also fails the other way: one crash involves a car that gave no warning and did not brake before hitting a stopped vehicle.

Three of the four reports involve crashes. The steering locks during a turn, or warning lights appear and the safety systems shut off at speed, and the car ends up hitting a wall or divider. One crash follows a loss of power on the highway combined with headlight failure at night. Owners also report lane keeping assist that fails to correct drift, and speed limit assist that slows the car sharply after misreading an exit sign.

No air bag deploys in either reported crash, and the two crashes involve three injuries in total. In one, a head-on collision in snow totals the car, and the occupant hits the windshield and dash. In the other, the car is hit from behind at about 40 mph while stopped at a light, and the dash then shows air bag fault messages. With only two reports, no broader pattern is clear.