Just purchased this car last week, the ABS light stays on and when brakes are applied they feel like they are, for lack of a better word, tapping. Brake fluid is ok, but the ABS reservoir is empty. I tried adding fluid to it, but can't see to get into it. In addition, when I first start the car the ABS motor hums, then stops, which is when the ABS light goes on. I'm hoping this isn't going to cost alot, and will just be something simple that I can do myself.