If your car is having a braking problem, whether it’s weak brakes, a mushy pedal, grinding sounds – whatever your brake problem is, you need to troubleshoot and repair it as soon as possible.
Even though your brakes operate in a closed system, contaminants can still work their way into the system. Air can enter the system through the smallest hole, and you can end up with water in the system from condensation and other means.
Your brakes should never wear low enough to cause your brake pedal to feel low, they’ll scream at you before then. But if they do get very low, you might have this problem.