Grinding/Abrasive Noise while foot off Gas pedal

[Underdog]

I also get the faint, high-pitched squeal when I let off the gas. Most noticeable with the windows down, and especially if I’m driving next to a surface that can reflect the sound back. Too consistent to call a rattle or screech, it sounds more like when a servo is hunting for position. If I give the car any throttle whatsoever, it goes away. In fact I thought maybe it was the throttle plate servo, but the wastegate could make sense as well. Do we know what about the wastegate design causes this noise?

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[polski]

When I coast it's a different noise all together. Coasting it sounds like when your brakes are wearing out and u get that noise to tell u it's time to change em. Everyone says it's the wastegate so I just deal with it

If the noise does not go away for you when you depress the clutch and is always happening like that it might just be a rock/pebble stuck between the heatshield and rotor.

 

[Victorofhavoc]

I also get the faint, high-pitched squeal when I let off the gas. Most noticeable with the windows down, and especially if I’m driving next to a surface that can reflect the sound back. Too consistent to call a rattle or screech, it sounds more like when a servo is hunting for position. If I give the car any throttle whatsoever, it goes away. In fact I thought maybe it was the throttle plate servo, but the wastegate could make sense as well. Do we know what about the wastegate design causes this noise?

Yes we do. Pop the hood and play with the wastegate by hand. You'll see it. There are two captive nuts that give about 1/16" tolerance to a metal bracket. That tolerance is what causes the bulk of the noise. The other end also has a loose rivet design and that also is part of it, but not as bad. Most other designs have the servo directly actuating a straight rod to the valve, but for some reason they decided to use a multipiece design in this case with some angle change. Not sure why they did this.

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