MY CAR MAKES A WEIRD NOISE WHEN I STOP. WHAT COULD IT BE?

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EVERYTIME I'M GOING TO MAKE A U TURN AND BRAKE AT THE SAME TIME IT MAKES LIKE A GRINDING NOISE, THAT SAME NOISE HAPPENS IF I GO DOWNHILLS AND TRY TO STOP. EVERYTIME THAT NOISE HAPPENS THE "ABS" LIGHT WILL TURN ON AND WHE IT HAPPENS AGAIN THE LIGHT WILL GO OFF. ALSO WHEN IT MAKES THE NOISE THE BRAKE WILL GET STUCK AND I HAVE TO PUSH IT 2 OR 3 TIMES FOR IT TO BRAKE. IT DOESN'T HAPPENS CONSTANTLY, IF I GO ON THE FREEWAY OR IF I DRIVE STRAIGHT I DON'T HAVE THE PROBLEM, IT ONLY HAPPENS WHEN IM DRIVING ON THE STREETS. I TOOK IT TO A MECHANIC, HE REPLACED THE FRONT BRAKES, BUT THAT DIDN'T FIX THE PROBLEM AND WHEN I TOLD HIM HE SAID THAT MAYBE I NEED TO REPLACE THE BRAKES ON THE REAR WHEELS, SO I DON'T THINKS HE KNOWS WHAT IS GOING ON. SOMEBODY ALSO TOLD ME THAT IT MIGHT BE THE BEARINGS? WHAT ARE THE SYMPTOMS FOR BEARING PROBLEMS? THANK YOU.