2018 BMW 3 Series Reliability Report

Stalling and getting stranded are the main risks. A failed high-pressure fuel pump can spread metal shavings through the fuel system, so the injectors, lines, pump and tank all need replacing. Other reports cover a faulty fuel level sensor that leaves the car stuck on the interstate, a collapsed filler hose that blocks refueling, and a fuel tank leaking at the top flange with no warning lamp. Coolant leaks from the cylinder head expansion tank hose also appear here, with overheating and reduced power that repeated dealer repairs fail to cure.

Coolant leaks lead again. The cylinder head expansion tank hose and a plastic coolant vent line leak, and the leaks sometimes return after a recall or bulletin repair. One car needed the fix twice by 26K miles. A cracked plastic oil filter housing causes overheating and can let oil mix into the coolant. Owners report this between 60 and 70 thousand miles. Other complaints cover a loud roaring sound with the rear windows down and a buzzing high-pressure fuel pump noise on unlock, which dealers call normal.

Stalling while driving is the main pattern. Cars shut off at highway speed or when coming to a stop, sometimes with drivetrain malfunction or transmission-not-in-park messages. One repair traced the stalling to a failed fuel pump and fuel rail that sent metal shards into the tank and injectors. Persistent coolant leaks with jerky running and repeated unsuccessful repairs also appear. One crash with an injury is tied to a rattling noise and a loss of control above 30 mph.

The repeating fault is a failed passenger seat occupancy sensor. A restraint system malfunction warning comes on, and the faulty sensor can stop the airbags from deploying. Repairs cost roughly two thousand dollars, and at least one car had under 34k miles. A separate report describes airbags that did not deploy in a front-left impact at about 45-50 mph, and the driver was injured. Owners note that BMW extends airbag coverage on some other models but not this one.

Unintended acceleration is the main concern. The car surges forward at low speed while parking, and one report links this to a collision with a parked car. A stuck cruise control rocker switch keeps raising speed past 80 mph. A third complaint is really about a run-flat tire that failed on the freeway, with severe vibration, pulling and grinding despite the reinforced sidewalls. Three complaints are too few to show a clear pattern.

Both complaints describe a sudden loss of steering assist. On the 330e plug-in hybrid, a charging malfunction message comes just before steering and brakes stop working at highway speed, and the car runs off the pavement. The other report describes a popping noise, then collision, steering and pedestrian warning lights, and steering that turns heavy as the electric assist drops out. Both carry a real loss-of-control risk.

Two unrelated problems appear. In one, the car lunges forward at a stop light while the brake is held, the pedal goes to the floor, and the car hits the vehicle ahead. That report is crash-related. The other is quieter but still risky: rear brake pads wear down to metal around 40000 miles with no brake wear warning. The wear is found only after a rubbing noise appears.