Different sound inquiry

Tara Martin · 10-05-2017, 12:05 PM

I have a 2017 ZL-1 M6 that was built in early April 2017. I now have almost 10k miles (I can't stop driving it!) About a thousand miles ago, I started hearing a "different" sound from the engine bay. For the first 9k miles, I would hear the supercharger whine when I cracked the throttle open, and I came to feel that it was normal as most of you do, I'm sure. Since about 9k miles, I now hear a continuous whine of sorts. It's hard to describe, but it's a cross between an old-style cavitating power steering pump and a cicada singing on a warm summer day. The whine follows engine RPM. At idle, it's not there. With the windows up and the sound system on, it's barely audible. Driving with the driver window down, you can hear the sound echo off of a nearby curb, building, or other structure. When I crack the throttle and engage a little boost, I don't really hear the supercharger as I used to because of this whine. There's no other symptom, and the car runs fine and strong as it ever did.

Does anyone have an idea what it might be? My air cleaner's full of cicadas and they're mad?

Am I just hearing the supercharger all of the time now? I hope it's not bearings or something.

I'll just sit here and

Thanks!

Tara

PS: I am the victim of both the rattling, loose sway bar endlinks, and the high riding front suspension. I plan on taking it in to get the front springs ordered in the near future.

bobby35ny · 10-05-2017, 12:51 PM

What exhaust mode are you running?
I noticed a kind of whistle in stealth mode.
-bobby

Tara Martin · 10-05-2017, 01:08 PM

Quote:

Originally Posted by bobby35ny

What exhaust mode are you running?
I noticed a kind of whistle in stealth mode.
-bobby

I 99% of the time run in Sport mode. It's definitely not a whistle.

Tara

kwav8r · 10-05-2017, 01:45 PM

Is the sound there when you get the SC into the boost side? Thinking it could be a wastegate flutter but I'm spit balling. Anyway you can record the sound and post?

Tara Martin · 10-05-2017, 02:59 PM

Quote:

Originally Posted by kwav8r

Is the sound there when you get the SC into the boost side? Thinking it could be a wastegate flutter but I'm spit balling. Anyway you can record the sound and post?

I would say yes. I can't hear the old spool up whine of the SC as clear anymore because of the cicada-like whine. I'll try to record the sound later on, possibly this weekend.

Thanks for any input!

Tara Martin · 10-05-2017, 03:00 PM

Quote:

Originally Posted by nancygrl

Tara, I think I'm experiencing the same thing. I'm at 5500 miles. Not sure what it is either. I will be checking a few things tomorrow and let you know if I find out anything.

Thanks!

Dethsupp0rt · 10-05-2017, 04:29 PM

Curious if it's the SC belt. The 'vettes are having theirs replaced. Description doesn't sound the same, but it's the only thing I can think of.

http://www.corvetteactioncenter.com/...-afm-1357.html

kwav8r · 10-05-2017, 05:04 PM

Quote:

Originally Posted by Tara Martin

I would say yes. I can't hear the old spool up whine of the SC as clear anymore because of the cicada-like whine. I'll try to record the sound later on, possibly this weekend.

Thanks for any input!

Looking forward to it. If you can, try and record different throttle positions (vacuum & boost).

Having said that, Dethsupport may be onto something with the pulley belt.

Gunkk · 10-05-2017, 08:24 PM

Bad idler pulley bearing?

Tara Martin · 10-06-2017, 07:16 AM

Quote:

Originally Posted by Gunkk

Bad idler pulley bearing?

I hadn't thought of that. I'll dig around under the hood this weekend. I've been so busy this week and last...

Thanks!

Tara Martin · 10-06-2017, 07:17 AM

Quote:

Originally Posted by Dethsupp0rt

Curious if it's the SC belt. The 'vettes are having theirs replaced. Description doesn't sound the same, but it's the only thing I can think of.

http://www.corvetteactioncenter.com/...-afm-1357.html

I'll definitely give mine a close inspection this weekend.

Thank you for any and all ideas!

Tara

17CamaroZL1 · 10-06-2017, 08:09 AM

Quote:

Originally Posted by Gunkk

Bad idler pulley bearing?

This was going to be my guess. Belt could also be a good possibility

BMWM.D. · 10-06-2017, 09:27 AM

I'd agree. Could be a worn belt, but there are a whole bunch of idler pulleys on the supercharger belt route.

I'm still not sure what's up with that service bulletin. It lists 2017 ZL1, but the main issue is related to AFM and noise when switching between modes. So that's a little odd. I just checked the belt on my 2018, and it's the same part number that came on the '17 models. So it doesn't look like a production change was made. What's also funny is that the Gates HD belt in that bulletin is longer than the stock belt. I'm not sure why. Usually that's the opposite of what you want to do to limit belt slip in a blower car.

That said, I decided to order a Gates RPM belt in the stock size. Why not? It should perform better and last longer than the stock belt. I figure having one in the garage isn't a bad idea.

Tara Martin · 10-06-2017, 09:44 AM

Quote:

Originally Posted by BMWM.D.

I'd agree. Could be a worn belt, but there are a whole bunch of idler pulleys on the supercharger belt route.

I'm still not sure what's up with that service bulletin. It lists 2017 ZL1, but the main issue is related to AFM and noise when switching between modes. So that's a little odd. I just checked the belt on my 2018, and it's the same part number that came on the '17 models. So it doesn't look like a production change was made. What's also funny is that the Gates HD belt in that bulletin is longer than the stock belt. I'm not sure why. Usually that's the opposite of what you want to do to limit belt slip in a blower car.

That said, I decided to order a Gates RPM belt in the stock size. Why not? It should perform better and last longer than the stock belt. I figure having one in the garage isn't a bad idea.

Good idea!

10-05-2017, 12:05 PM	#1
Tara Martin Loves Camaros Drives: Red '79 Z28, '21 Red Hot M6 ZL-1! Join Date: Sep 2012 Location: Corpus Christi, TX Posts: 1,622 View My Garage	Different sound inquiry I have a 2017 ZL-1 M6 that was built in early April 2017. I now have almost 10k miles (I can't stop driving it!) About a thousand miles ago, I started hearing a "different" sound from the engine bay. For the first 9k miles, I would hear the supercharger whine when I cracked the throttle open, and I came to feel that it was normal as most of you do, I'm sure. Since about 9k miles, I now hear a continuous whine of sorts. It's hard to describe, but it's a cross between an old-style cavitating power steering pump and a cicada singing on a warm summer day. The whine follows engine RPM. At idle, it's not there. With the windows up and the sound system on, it's barely audible. Driving with the driver window down, you can hear the sound echo off of a nearby curb, building, or other structure. When I crack the throttle and engage a little boost, I don't really hear the supercharger as I used to because of this whine. There's no other symptom, and the car runs fine and strong as it ever did. Does anyone have an idea what it might be? My air cleaner's full of cicadas and they're mad? Am I just hearing the supercharger all of the time now? I hope it's not bearings or something. I'll just sit here and Thanks! Tara PS: I am the victim of both the rattling, loose sway bar endlinks, and the high riding front suspension. I plan on taking it in to get the front springs ordered in the near future. __________________ Old and new, sharing space!

10-05-2017, 12:51 PM	#2
bobby35ny Drives: 18 ZL1 A10 Join Date: Nov 2008 Location: South East, FL Posts: 3,024	What exhaust mode are you running? I noticed a kind of whistle in stealth mode. -bobby __________________ 2017 ZL1 M6 Bog City, 2013 ZL1 M6, 2010 2SS M6 ZL1::J-E-T-S JETS JETS JETS

10-05-2017, 01:45 PM	#4
kwav8r Flyin NOE Drives: 2018 ZL1 (A10) Join Date: Apr 2017 Location: TX Posts: 949	Is the sound there when you get the SC into the boost side? Thinking it could be a wastegate flutter but I'm spit balling. Anyway you can record the sound and post?

10-05-2017, 04:29 PM	#7
Dethsupp0rt Drives: None Join Date: May 2017 Location: Chicago, IL Posts: 462	Curious if it's the SC belt. The 'vettes are having theirs replaced. Description doesn't sound the same, but it's the only thing I can think of. http://www.corvetteactioncenter.com/...-afm-1357.html

10-05-2017, 08:24 PM	#9
Gunkk Thank you Al Oppenheiser! Drives: Red Hot A10 ZL1 Convertible Join Date: Jun 2017 Location: Sarasota, FL Posts: 4,973 View My Garage	Bad idler pulley bearing?

10-06-2017, 09:27 AM	#13
BMWM.D. Drives: ZL1/335i Join Date: Apr 2014 Location: Santa Barbara Posts: 870	I'd agree. Could be a worn belt, but there are a whole bunch of idler pulleys on the supercharger belt route. I'm still not sure what's up with that service bulletin. It lists 2017 ZL1, but the main issue is related to AFM and noise when switching between modes. So that's a little odd. I just checked the belt on my 2018, and it's the same part number that came on the '17 models. So it doesn't look like a production change was made. What's also funny is that the Gates HD belt in that bulletin is longer than the stock belt. I'm not sure why. Usually that's the opposite of what you want to do to limit belt slip in a blower car. That said, I decided to order a Gates RPM belt in the stock size. Why not? It should perform better and last longer than the stock belt. I figure having one in the garage isn't a bad idea.

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