The Office of Defects Investigation (ODI) has identified 32 complaints alleging electric vacuum assist pump failures resulting in loss of brake power assist and increased brake pedal effort in model year (MY) 2011-2012 Ford F-150 full-size pickup trucks equipped with 3.5L GTDI engine. None of the complaints reported any warning indicators to alert the driver of brake power assist loss or the potential of increased stopping distance. Two reports alleged crashes due to increased brake pedal effort required to stop or slow the vehicle. The complaints show an apparent increasing trend, with approximately 60 percent of complaints received within the past nine months. A Preliminary Evaluation has been opened to assess the cause, scope and frequency of the alleged defect.