Help! My brakes!

Hi to all. So my brakes aren't working properly. When I apply pressure to the brake pedal , I can hear air, a sort of hissing sound from behind the brake pedal. I don't think it's the booster or master cylinder because I'm not losing any brake fluid and the bake pedal isn't high or hard. The brakes pads are new. So it's not that. And the hissing sound makes me suspect an vacuum leak maybe? Should I bleed the brakes first? Any help to help me find and diagnose the problem,any insight or suggestions are greatly appreciated. Go easy on me, I'm a woman😜

A bad booster wouldn't necessarily cause a fluid leak and it may cause that hissing sound. It could also be air in the brake lines. Start by bleeding the brakes and if that doesn't work, check the booster.

Thank you. If it were the booster wouldn't my brake be high and hard? Or is that not always the case?

Thank you. If it were the booster wouldn't my brake be high and hard? Or is that not always the case?

Not necessarily. In the case of an immediate catastrophic failure of the brake booster, yes the pedal would get stiff and hard to operate. Sometimes the brake booster starts acting up gradually. For a while it will still sort of work, just not as well as it should.