Weird sound when I shut the truck off. Sounds like the brake booster is bleeding off air kinda like an air compressor sounds like. It also makes the sound when I blip the throttle a little and then it goes away until I do it again..... Anyone else know this sound and how to fix it?

 

If it does it when you hit the throttle I don't have a clue how that would be a brake problem. It's most likely AC or something.

 

The brake booster makes the hissing sound...... That sounds like brakes to me.....LOL

I need to point out that it is clearly coming from the brake booster when I start the truck with the hood open and shut the truck off and listen to it. It's a hissing sound that sounds like an air compressor tank makes when you let the the air out of it. Not the sound the hose makes, but the sound the tank makes.....

 

ttt bump

 

Nobody?

 

Are you sure you don't have a CAI and that is making the noise?

If not, your pcv valve maybe completely clogged. That's where i would start.

 

mine makes the same hissing sound, but it is coming from the ac. it is just decompressing... it only does it if i had the air on, or the defrost on. try turning your air and defrost off, see what it does

 

vacuum drops when the throttle is opened. I've seen a few boosters go bad and sound like that.