High pitched whining noise only past 10vac

[eboy0]

Don't understand what's going on, if i boost the car, nothing is wrong... it's only when i let off the gas pedal and boost gauge goes past 10vac where i start to hear this high pitched noise. I checked for shaft play, none.... was the first thing i thought it was, since it does sound like metal on metal noise.... can't figure it out guys.
Can this be a very small boost leak? I boost leak tested the system, get it up to 18 psi, then it slowly starts to drop.
Help?

 

[Loewen21]

could it be a loose or popped of vaccum line? mayb cracked even? just an idea

 

[Rex2342]

Does it sound more like a whistling noise? I can think of anything that would make a metal on metal sound that would have anything to do with vacuum. If it's more of a whistling sound it's probably just your BOV leaking or a possible leak somewhere else. Mine will make a whistle sound at 20vac because of the BOV and I'm running a crushed 1g.

 

[92AndAHalf]

I'm running a vented TurboXS BOV and mine does this as well when i let off the gas. Almost sounds like the whistling of a tea kettle and changes pitch as the BOV piston seats itself back down.

 

[eboy0]

I'm running a vented TurboXS BOV and mine does this as well when i let off the gas. Almost sounds like the whistling of a tea kettle and changes pitch as the BOV piston seats itself back down.

That's what it sounds like! A tea kettle, i couldn't figure out what it sounds like... but you got it.

 

[andymoraitis]

That sounds like a vacuum line leak.

Run the motor at idle and spray each line with carb and choke cleaner while listening for changes in the idle. If you find any hoses where spraying creates a change then change the line. As a matter if fact it's not a bad idea to replace all of them if it's never been done before.

Your local auto parts store will have everything you need.

Also, I know you ran a leak test, but how long did it take for the system to bleed down to zero?

 

[eboy0]

That sounds like a vacuum line leak.

Run the motor at idle and spray each line with carb and choke cleaner while listening for changes in the idle. If you find any hoses where spraying creates a change then change the line. As a matter if fact it's not a bad idea to replace all of them if it's never been done before.

Your local auto parts store will have everything you need.

Also, I know you ran a leak test, but how long did it take for the system to bleed down to zero?

What exactly do you mean each line?
Took about 30-45 seconds to bleed out to 0.

 

[andymoraitis]

Each line means every vacuum line. If your boost held for 30-45 seconds, we can definitely rule out boost leaks.

 

[92AndAHalf]

When I first heard this noise, I popped the hood and revved up the car a bit until I heard it. Luckily my BOV is facing up so I can see the piston moving. Didn't take much to bring the piston off it's seat, and when it was very partially open it would make the tea kettle whistling.

 

[WeaselHack]

My money is on a collapsing vacuum line. I had this issue after changing to a weafy PCV line. It would collapse and sound like a tea kettle anytime below 13 inHg of vac. Since you have checked for boost leaks, this could explain the noise. Just let the car idle, pop the hood and listen around the engine bay. You'll find it - Good luck!

 

[Rex2342]

It's just your BOV whistling. Mine does it too as does allot of others. If your that worried about it just adjust your BOV by packing more washers to stiffen up the spring. Use a vacuum pump and pack washers into it until it opens at around 18-20 inches of vacuum. It may or may not still whistle but at least you'll know it's working properly. This link is a guide to crushing a 1g BOV but it's essentially the same idea. You'll just be able to add washers to stiffen it up instead of crushing it. http://www.geocities.com/MotorCity/Garage/8384/crushBOV.html