Most likely, this sound is coming from a vacuum leak in your brake servo, or brake booster. Which are usually located on the firewall, the wall that divides your engine compartment and cab.
brake booster could be bad the seal around the rod that hooks to the brake pedal is leaking
cheack your break booster.
Replace your brake booster.As it sounds like it is leaking. Costs about 150.00 and relativly easy to install.
The brake pedal has nothing to do with it. If air is in the system then bleed the brakes.
The power brake booster is bad.
You may be able to adjust the pedal. You might also have air in the hydraulic line and need to get the air out.
dude! sounds like air brake sys.(system needs to be bled get air out of sys.)As for gettin stuck , check linkage,brake booster and master cyl.
Hardness in the brake pedal can because by low brake fluid. Air in the brake lines can also cause the pedal to push hard.
The power brakes on most vehicles operate on the engine vacuum. If there is a leak or problems with the power brakes it can make a hissing sound. But then, sometimes power brakes do that when they're working properly. It could be from either a hole in the diaphragm of the brake booster or normal operation. If the sound is new, and was not there before, and your brake pedal is going to the floor, then you should have the power booster replaced.
It seems like there might be air in your brake system. You should try bleeding your brakes and filling it with fresh brake fluid.
air in the brake lines theyneed bleed