Steering Column problems of the 2004 Lincoln Navigator

The contact owns a 2004 Lincoln Navigator. The contact was driving approximately 15 mph when the steering column locked and then the steering wheel turned in the right position without warning. Suddenly, there was a loss of steering control and the vehicle traveled over a curb up an embankment. When the brakes were engaged the vehicle came to a stop. The vehicle was driven from the embankment and the identical failure reocurred. The vehicle was taken to a nearby independent mechanic for diagnosis. The vehicle was taken to the dealer where they were unable to duplicate the problem. There were unrelated repairs performed on the vehicle. The failure mileage was approximately 67,000. The VIN was unavailable. The contact had concern of the potential safety hazard.