The agency says it has 33 complaints about the problem, including some drivers reporting that the pedals can suddenly go to the floor with a complete loss of braking. Four drivers reported that the problem caused crashes, although there were no injuries. The agency reported that 31 of the complaints from F-150 drivers came in the past year, with 20 in the past seven months.
Some of the drivers reported that mechanics told them brake fluid had leaked from the master cylinder to the brake booster, causing the problem.
Ford said it takes customer safety seriously and will cooperate with the investigation. Trucks with other engines could also be covered by the probe. Ford says F-150s with other engines have the same braking system.
One owner from San Marcos, California, told NHTSA that he was backing his pickup out of the driveway in May of 2015 when the pedal went to the floor and he completely lost his brakes. The pickup crossed the street, went over a curb and hit a neighbor's landscape wall, causing severe damage, the driver wrote.