Why do I "hear" air when I step on my brakes?
98 gmc truck, pedal goes soft, than hard.
Sounds like your Master Cylinder is low on fluid or on it's way out ! You might try bleeding the brakes though, just in case . Master Cylinders aren't cheap .
Does it take a while for the car to stop? Do u have to really step down far for it to stop?
I know it sounds wierd but its because there is water in ur brakes
The air could be as a result of a bad power booster or the vacuum lines are damaged. It could also be that the valve or master cylinder is bad. You need to contact a mechanic so that he can identify the problem and fix it for you.
Power booster no good resulting in the vacuum hissing noise you hear. Replace brake booster