I am hearing hissing noise from the pedal area.
My car has an automatic transmission.
Hi there - your brake power booster has failed - specifically the internal diaphragm. That unit uses engine vacuum for braking assist, but when the diaphragm ruptures as yours has, it sucks in air from inside the passenger compartment. You have probably also noticed that it take much higher brake pedal effort to stop your vehicle. I would recommend replacement of the brake booster by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.
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