Brake Master Cylinder problems of the 2010 Lincoln MKS

The contact owns a 2010 Lincoln Mks. The contact stated that the vehicle failed to respond to deceleration attempts. The vehicle was taken to the dealer who diagnosed that the brake booster needed to be replaced. The vehicle was repaired but the failure recurred. The vehicle was taken back to another dealer who determined that the master cylinder needed to be replaced. The remedy failed to repair the failure. The manufacturer was made aware of the failure. The failure mileage was 16,000 and the current mileage was 19,700.

Brake pedal invariably collapses completely to floor when they are depressed causing the brakes to not properly function. This typically occurs upon startup, when the brake pedal is depressed in order to move the gear selector. I have experienced this problem over the course of several months. Other operators of the vehicles have noticed a clicking or popping sensation that could be felt by the driver during depression of the brake pedal. I decided to carry the car to the dealership after experiencing total brake failure temporarily while operating the vehicle on the highway. Due to the sudden lane intrusion by another vehicle, which required emergency braking and maneuvering, I experienced substantial underperformance of the brake system during brake pedal depression; there was very little brake pedal pressure. During this particular event, I experienced very similar brake pedal depression that I invariably experience during startups. The vehicle was taken to the local Ford dealership, where a defective master cylinder was diagnosed as the problem. However, the car was subsequently returned to the dealership (where it remains at this moment) because of recurrence of the brake pedal problem and improper braking system, which makes the car unsafe to operate. The dealership was unable to replicate the problem over the course of more than a week and informed me that they could not find anything wrong with the brakes. My concerns have been elevated to dealership management.