The contact is calling on behalf of her grandson for a 2015 Kia Optima. The contact stated that while he was driving at approximately 35 MPH, the vehicle was making an abnormal sound and stalled. The contact stated he restarted the vehicle and was able to shift to drive (D), but the vehicle again stalled. The contact stated that he observed that white smoke was coming from under the hood. The contact stated that he pulled over and stopped the vehicle, opened the hood, and saw that smoke and flames had formed under the engine. The contact stated that he called the fire department. The fire was extinguished using foam. The vehicle was towed back to the contact's residence. The contact had not called a dealer or the manufacturer. The vehicle was not diagnosed or repaired. The contact had researched online and related the failure to NHTSA Campaign Number: 21V331000 (Service Brakes, Hydraulic). The contact stated that her grandson had not received a recall letter from the manufacturer. The failure mileage was 158,006.