2001 Grand Cherokee brake issues

I have a 2001 Jeep Grand Cherokee with 43,000 Km's 6 cyl power everything. The brakes will just fade to nothing and I am left with no brakes at all. This is the third time that this has happened to me. The first time the dealer told me that the pads were done up front and that it was a fluke that the brakes faded that bad. they replaced the pads under warrenty and adjusted and cleaned the rear. The seconf time it happened the brakes let go during a hard stop. The pedal went to the floor and there was no braking left. The dealership replaced the master cylinder and cleaned and adjusted the brakes at all corners. The tech said that he checked the antilock system and there was nothing wrong. I asked about recall's and was told that there were none for this problem. The Jeep was fine for about a month and two days ago the brakes went agian during a hard stop. The dealer towed the Jeep in and I told them that I did not want it back unless it was fixed in fear of loosing braking and not being able to avoid an accident. Any help would be appreciated..