Engine Knocking Noise problems of the 2007 BMW Z4

The contact owns a 2007 BMW Z4. The contact stated while driving 70 mph, there was an abnormal knocking sound coming from the engine. The contact pulled the vehicle over to the side of the road and inspected under the hood and underneath the vehicle. The contact found no issues. There was no warning light illuminated. The vehicle was towed back to the residence. The vehicle was next towed to the local dealer BMW dealer to be diagnosed. The mechanic was unable to determine the cause of the failure. The vehicle was not repaired. The manufacturer was made aware of the failure. The failure mileage was 81,000.