1997 GMC C1500 noise

can you describe what a vaccum sound is like? do you notice any decrease in the performance of the brakes?

have you noticed any issue wiht the performance of the vehicle?

does the sound you hear such as when the engien is off and you push on the brake pedal, is that the sound your hearing?

I hear it both times when using the brakes and also when the car is shut off

but what is the sound? i dont know what you mean by vaccum.

Kind of like a hissing sound, even when I step on the brakes I hear it.

you notice any decrease in brake performance as prevously listed.

the brake level still good?

the brake is very hard to press, before I could press them and stop on a dime if needed. I need to put a lot of pressure on to press it down now. It is not always making the noise when I step on it. But when it does it kind of sounds like something letting air out.

sounds like a bad brake booster or possible bad check valve in it.

which would explain the hard to push pedal and noise when pushing on the brake.