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? :iono: 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 :popcorn:

Thanks!

Tara :wub:

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. :dizzy:

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. :whistle:

Tara :love:

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!

Thanks!

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

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.

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!

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

Thank you for any and all ideas!

Tara :wub:

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

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! :thumb:

This should be a sticky-(Gates Belt #)

I ordered one of the green (HD) belts listed in the bulletin, but I'm not convinced that's the best option. At least for maximum belt grip and performance, I think a Gates RPM belt in stock length is a better choice. I've used the green HD belts in the past, but this was before the RPM line was introduced. And unless you're experiencing this exact noise (which shouldn't affect ZL1s without AFM), I'd stick with a stock length belt. Just my 2 cents after building a bunch of blower cars and fighting belt slip.

For anyone interested, the Gates RPM belt in our stock size is: K080828RPM. The stock belt is GM part number 12668317.

Good info, subscribed. :popcorn:

Hey Tara,

We understand how this noise can be frustrating and would like the opportunity to review this further with your preferred dealer. Could you please send us a private message with your contact information, VIN, and dealer information? Once we receive your message we'll follow up there and move forward with getting an appointment set up. Feel free to let us know if you have any questions.

Sincerely,

Eddie A.
Chevrolet Customer Care

I hope this works out. Wish me luck with my whiney, clunky, and high-riding front end!

Tara:wub:

Hmmm...this was a peculiar thread for Customer Service to take an interest in....

:rules: The girls always get the attention!

Tara is our hero!! :thumb:

Hah! I hope so! No word yet.

Tara:love:

Travis - Maybe we should have Tara check in on the launch issue. ;)

Welll, almost two days has passed since I supplied my info as requested above, and I've heard nothing.

:noidea:

Tara

Hi Tara,

Thanks for sending us the requested information. We've opened up case 8-xxxxxxxxx documenting this concern in our system. We'll be forwarding this case to a a specialist that'll be in contact with you within the next 48 business hours. Also, our internal resources will be reaching out to your dealership to assist them with the diagnosis. Please let us know when you've been contacted by the specialist, and we'll provide you with another update after we touch base with the Customer Experience Manager at Aztec Chevrolet. If you have any questions in the meantime, feel free to let us know. We appreciate your patience with this matter.

Sincerely,

Eddie A.
Chevrolet Customer Care


Hmmm, does 48 business hours = 6 business days? They might call me by October 23rd? I'm confused. I hope they call...

Tara:love:

Update!

A Chevrolet CSR contacted me yesterday and we together contacted my dealer's service department. We've tentatively set up an appointment for Thursday afternoon pending the availability of a loaner vehicle. The service fellow was able to find GM documentation of the ride height issue and the front sway bar end link nuts. A while later he called me back and said that he found an issue that GM engineers are investigating concerning excessive supercharger whine. He said it wasn't finalized into a TSB, but Chevrolet says it's safe to drive until they arrive at a fix. He also confirmed that he had ordered the springs and sway bar nuts and hopes that they arrive by Thursday.

I see that there's another thread recently describing a RPM-related whine from the engine compartment. I wonder if it's the same thing I'm hearing...? :confused:

So far, so good! :cool:

Tara :love:

For the record, there is no such thing as excessive supercharger whine. ;)

Hah! :pound: Mine echoes of off curbs and walls! :director:

Tara :wub:

Hah! Yeah, I blew by a car the other day with my window down, and I was just about deaf in my left ear for a bit. The CAI is worth it for this alone (although I still wish it was louder).

:thumb:

Update:

No appointment tomorrow. The front springs are on back order, but the swaybar end link nuts came in. Service manager hopes that the springs will be here in a week. Reschedule then.

Original problem, whine under the hood, appears to take a back seat until Chevy/GM engineers figure out the issue and formulate a fix. I was told to keep driving the car as it won't cause any long term problems. :popcorn:

Tara :wub:

Update:

Part came in yesterday (front springs.) Service Dept made an appointment for me for Tuesday afternoon after I get off. It appears they won't have a loaner until then. Still nothing on the whine, although I think it's getting louder. Car still drives fine with no other symptoms.

See y'all!

Tara :wub:

I agree with the idler pulley idea, and the serpentine belt is a possibility. Needs audio/visual inspection.

See if the noise stops instantly when you push in the clutch - if yes - throwout bearing

j

I'm glad you got that figured out! Mine is definitely engine-speed related. Service manager sounds like he's motivated. I'll see what he thinks on Tuesday at my appointment.

Tara :wub:

Wish me luck! I'm scheduled to take her in tomorrow after work.

Tara :love:

I dropped her off on Tuesday afternoon after work. Service Dept called a bit ago that she's ready for pickup. They replaced the front springs and the sway bar end link nuts. They couldn't find an update for the engine management computer (they say...) The cicada-like whine is a know issue, but has no resolution yet. They say Chev/GM Engineering is studying it, but it's okay to drive with no issues.

A friend of mine floated the idea that the way the gears might be cut in the SC might cause a difference in sound as everything breaks in together, but that's just a guess.

I'm picking her up right after work and will report back my experience probably tomorrow.

Take care,

Tara :love:

I picked up my Z on Friday late. Service Manager placed my key fob in my cupholder. My front springs were replaced as were the front swaybar endlinks. The loud whine noise is said to be an GM engineering study still and they'll notify me if there's any updates or a TSB. They said to report any change in the sound back to them.

I'm waiting for the springs to settle a bit before I measure ride height again.

But...I get home from dealer on Friday night. I get my key fob and put in my pocket and don't notice until Saturday that the little chrome/gold Chevy bowtie is missing off the fob! There's just a dull piece of plastic where the emblem was. The car and fob are only 6 months old. Chevrolet Customer Service called me on Monday about my dealer visit and I told them about the fob, but they said it's not under warranty and is considered a wear item. Pfft! It was apparently damaged outside of my control while it was at the dealer. I've been trying to get in touch with my salesman to see if I have any recourse other than to replace it...not that I need to as it still functions 100%...

Venting, I am... :sad0147:

Whining noise
 

Not sure if your problem was solved but one of the members were correct with their with opinion on the idler pulley bearing, at least that was my problem with the constant whining noise and certain RPM's. Also at the bottom of the invoice you'll see a recall on a harness for the instrument panel that they ordered for me.

I just started having increased noise from under the hood this week (8300 miles), it sounds like a pulley/bearing problem to me. I also had the swaybar klunking.


Is your problem resolved? I'm going to schedule an appointment for my car next week.

yes problem resolved