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Q: The brakes are spongy while the car is running but the pedal is normal when it's off

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My mom was coming over a bump the other day and when she got to the top she hit her brakes and they went out she could still use them but she would have to crush them always down the master cylinder was replaced and bled where's new brake fluid and now it gets hard when it's off but when you start it new releases it becomes spongy again the rotors are a little worn but I'm not sure if that could affect it

My car has 145000 miles.
My car has an automatic transmission.

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