weird hissing sound?

[WhiteZ34]

I just noticed tonight on my way home from work that when I press down the brake petal I hear a hissing sound. It isn't very lound but just enough to get me worried. Also once I got home and had the car in park when I pressed on the petal along with the hissing my idle went up just a little.
Any thoughts? BTW it's a 92 Z34 Auto if that helps.

Mike

[WhiteZ34]

Hey everybody, Just to let you know it was the brake booster. So if you start to hear a hissing under the dash when you press on the brakes go get a replacement quick. My power brakes were gone only after about an hours driving time after hearing the sound and to top it off it somehow was managing to push air into the engine making braking that much more difficult.

Mike

[RednBlack]

Hey everybody, Just to let you know it was the brake booster. So if you start to hear a hissing under the dash when you press on the brakes go get a replacement quick. My power brakes were gone only after about an hours driving time after hearing the sound and to top it off it somehow was managing to push air into the engine making braking that much more difficult.

Mike

Well, you are half right. What you hear is vaccum being taken away from the engine, not air being pushed into it. Hence, your idle going up.

[WhiteZ34]

Thats what I meant the vacume leak would open up when the petal was pressed on letting air in the engine. Good catch.