2019 Mercedes-Benz GLC Reliability Report

Two failures stand out. The more common one is the crankcase ventilation valve, which sets code P052E, lights the check engine lamp, blocks emissions inspections, and costs over $2K to repair. It shows up around 52,880 miles. The more serious one is a cracked or broken piston, which causes violent shaking or a sudden loss of power at highway speed with no warning light. One owner was told the engine needed replacing at 52,839 miles, just past the 50,000-mile warranty.

The transmission can hang in neutral when shifted from reverse to drive. It then stalls or jerks into gear, and one dealer blamed the valve body and low pump pressure. Another report describes the car dropping from highway speed to about 15 mph without warning because of a front differential failure. The car also rolls back on hills, lurches forward while the brakes are applied, and jerks when braking. On plug-in hybrid models, overheating is reported. Dealers often cannot duplicate these faults or call them normal.

The front wheels skip, judder, and knock when the steering is turned sharply, most often when backing out of a parking space. Drivers say it sounds and feels like hitting something, and some worry an axle will break. One high-performance model also has steering wheel shake and wobble in turns. Dealers have called the behavior normal even after reproducing it. No repairs are reported, and the complaints do not show a clear mileage pattern.

The car surges forward without warning during slow driving at about 5 to 15 mph. Both complaints in this category involve crashes with injuries. In each case the vehicle jumped a curb, hit a street sign, and struck a concrete planter, and the airbags deployed. No warning lights came on beforehand. One owner says the event data recorder showed the accelerator at 100% even though they were only pressing it lightly. The cause is not established in these reports.

The front stationary sunroof panel separates from the roof and flies off at highway speed, which ties into the roof problems reported elsewhere. The other complaint is about a driver's window switch that breaks apart in the hand while the driver is trying to clear a fogged window in the rain, at about 27,500 miles. The manufacturer opened a case but later declined to help, and the car was not repaired. Only two complaints fall in this category.

The rearview camera stops working and shows no image when the car is put in reverse. No warning light appears. In one case a dealer said the backover prevention software needed an update, but the VIN was not covered by recall 22V232000, and the car was not repaired at 76,954 miles. Owners call it a collision risk for pedestrians and other cars. This category has only two complaints.

The moonroof glass shatters while driving at around 35 mph with no impact, matching the roof failures in other categories. The windshield wipers skip across the glass at all speeds and leave the view unclear in rain. Replacing and adjusting the blades does not fix it. The manufacturer has called it a known problem with no fix yet, and owners report that no aftermarket blades fit.