Power brake assist sometimes is not available. The car is very hard to stop. My wife could not stop it. Called Ford dealer and explained the problem after about 8 failures. Ford says that they cannot fix without codes. Sometimes when first starting the car, power brake assist would not be working and then I would hear a high pitched metallic sound and the power assist would start working.

They drove car and said they did not have problem. Ford claimed that they have not seen problem. Other complaint on brakes on same car says that the car is hard to stop in traffic. It sounds like the same problem. Ford dealer wanted me to drive car until it happens again. This is a dangerous situation. They are keeping car to see if it happens again.

Called the Ford representative and it appears to be a no action listener. Could not get telephone number of local Ford representative from customer service representative. The system is obviously not failsafe and I told Ford representative that Ford Corp should warn customer. Doesn't sound like they care. Ford would only give case number and confirm complaint by email. Sound like they want no paper trail on complains. Sorry I don't have vin number because Ford dealer has car. I question capability of Ford mechanics factory training if they can only fix the problems if code shows tells w them what to do.

Update from Jan 10, 2018: Had to argue with Ford dealer to fix the problem. Had to agree to pay for diagnosis if my fault, they first claimed that rodents may be the problem since I kept the car in my garage for a few days at a time. Them they said that there were no codes so there was no problems. They refused to give me a signed paper that the car was safe to drive. I had to tell them to contact Ford for a solution. Ford sent them a procedure to use smoke to test the vacuum booster. It failed. It then took three weeks more weeks for a revised vacuum booster to be installed. I think that there is a serious brake problem with these cars and Ford is trying to hide it. If anyone has one of these cars, do not drive very close to other cars and start to stop about three times further back. You can't tell when the original vacuum booster will fail. Others have reported similar stopping problems. Also, I call the 800 number for a Ford representative and asked them what they were going to do about it. They gave me a claim number. I think that Ford only pretends that you can call in a complaint.