I`m having a real bad time with my truck. For the last 2 months or so I have had a high pitch metal noise at idle after I put the truck in park. I finally know where its coming from, but don`t know how to fit it. The noise is coming from the power brake booster. If I disconnect the hose & plug it up no more noise. So I put a new booster in & the noise is still there. So my Dad has a truck that doesn`t make a sound in his booster so I switched with him. Guess what the noise is still there too!!! But if you plug the booster off so no vac. is there the noise is no longer there.So I need HELP in a big way I don`t want to keep throwing money away!!!And I want to keep my truck , there has to be a answer Or a fix. PLEASE!!!! Someone help me. I`ve checked the vac. its fine 20 in. on the gauge. The truck runs fine. But the high pitch drives me nuts!!! You can only hear this noise if the windows are up , the radio is off, the panel switch is off. When you slow down to stop you hear it a little, & then when you put the truck in park it there ringing again. HELP!!!!!

 

What year truck?
Is it a screeching sound or a high whistling sound?If it whistles,its a vacumm leak some where. Good luck,thats a weird one allright.