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Question: My right rear wheel has locked up and whenever I drive it a terrible screeching noise comes from it.

Well a week ago when I was driving my car I heard this popping noise,
so I pulled over to see if I'd blew a tire but I hadn't. So when I start back to driving my car the brakes lost tension and I had to push the
pedal all the way to the floor to make it stop. I took it to a mechanic
and he said I just needed brake fluid and it would be okay and it seemed to be fine after that. Well today I was pulling out my driveway and I
heard this awful screeching/howling noise and then someone who was
outside told me that my wheel wasn't spinning. So I have no idea what's
wrong with my car.
only thing I can think of(research) is either the brakes or wheel bearings.