Two problems related to brake master cylinder have been reported for the 2010 Jeep Wrangler. The most recently reported issues are listed below.
Attempted to stop at a traffic light and the brakes would not work. Brake pedal went all the way to the floor but nothing happened. Tried pumping but nothing. Ended up running the red light and was not able to get it to stop until I had crossed through all the lanes to the other side. Brakes started working after crossing the street and continued to work until taken back to Jeep service. They replaced the master cylinder and brake fluid. Found internal failure of brake master cylinder, installed new one and bleed master cylinder. Evidently there was a recall on the 2010 master cylinders but my Jeep did not receive a recall notice. How do I know that the master cylinder was replaced with a new type and not the same style master cylinder that failed.
After driving on the freeway for approx. 40 miles I attempted to exit. I applied my brakes to start slowing down and proceed to get into the exit lane. Once in the exit lane I tried to apply more brake pressure to slow down faster, and the brake pedal slowly traveled all the way to the floor. I managed to get back on to the freeway without incident and onto a breakdown lane to slow down. I applied my brakes again, and after applying a moderate amount of pressure the brake pedal continued to travel to the floor. Using only moderate brake pressure I was able to slow down my vehicle and stop. Any more than moderate pressure would cause the pedal to go to the floor. I checked my brake fluid level, and it was still at the max level, so I proceeded to pump my breaks to try and locate a leak. There were no leaks and the brake fluid level did not go down. I slowly continued home knowing that I had limited braking ability. At home I inspected my vehicle again, and there was no brake fluid loss. I opened the brake fluid container and inspected the fluid level, the fluid level was at the max mark, but I noticed small black particles at the bottom of the container. I called the dealer I purchased the vehicle from and described the incident. They picked up my vehicle and replaced the brake master cylinder.