The brake pedal goes soft, but I can pump up the brake.
I have seen this before. It is usually caused by an internally leaking master cylinder. The master cylinder is where the pressure for the entire brake system is developed. If it leaks internally, your pedal goes down, if you release it and step on it again you can build up some pressure. Eventually if you keep your foot on the pedal, it will go down again. Replacement of the master cylinder is the usual repair. This requires opening up the hydraulic system and bleeding any air that may be trapped in the lines. Not doing so will leave you with a very spongy feeling pedal. I suggest seeking the help of a qualified mechanic, such as one from YourMechanic, to help you.
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