When I press on the brake, sometimes it is hard to press down. Then when I push real hard, it goes back to working fine temporarily. It sounds like I'm letting air out of something when I press on the brakes. If I press real hard, it makes a screaming noise.
It sounds like your brake booster is worn out. There is a diaphragm inside the booster that wears out and will not allow the booster to get enough vacuum to work properly. I would have a technician from YourMechanic come out and perform a brake inspection and inspect the brake booster.
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