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.

 

[Underdog]

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.

Thanks I will check it out.

 

[dockleryxk]

like something brushing against something else like medal on something abrasive

this is exactly what is happening – the wastegate opens and a little metal doohicky rattles around and sounds crazy

 

[polski]

this is exactly what is happening – the wastegate opens and a little metal doohicky rattles around and sounds crazy

Ahh got it. If that's the case and this is "normal" for this car then I will live with it. I kow when I had my MK7 GTI that had its quirks also were just something that you needed to live with. As long as it doesn't affect driveability/reliability.

 

[Underdog]

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.

Observed this while I had the hood open yesterday and rattling it around by hand, the pitch matches what I hear when coasting. I only looked briefly but it seems maybe just adding a little mass to it might cut down the vibration. Or maybe a little hi-temp anti-seize on the interfacing surfaces? The slop looks like a result of cost-cutting rather than accommodating misalignment in the wastegate mechanism.

 

[Victorofhavoc]

Observed this while I had the hood open yesterday and rattling it around by hand, the pitch matches what I hear when coasting. I only looked briefly but it seems maybe just adding a little mass to it might cut down the vibration. Or maybe a little hi-temp anti-seize on the interfacing surfaces? The slop looks like a result of cost-cutting rather than accommodating misalignment in the wastegate mechanism.

Yeah.... That was about my interpretation as well. I've been accused on this forum of being a bit too critical of this car/platform and its build quality issues, so I've tried to allow others to come to their own conclusions more.

My friend wanted to add a stainless washer to the captive nut and then dropped it into the engine bay, so now that's somewhere deep in the plastics, . The captive nut is also super hard to turn unless you have a set of tightspot, swivel head, ratcheting wrenches.

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