Strange noise during warm-up

Lilwilly · 05-03-2021, 05:37 PM

I’m reaching out to see if anyone might have had the same issue with their car. I have a 2021 ZL1 that I bought new in February and have been putting the break-in miles on the car. I noticed from day one that I’d get a sound like a low pitched squeal or a idler or belt tension pulled going bad. This would only happen on the first start of the day and last until the car was warm. It varied with engine speed, but went away above approx 1300-1500 RPMs. Today I started trying to find the cause and noticed if I manually move the boost bypass valve, the sound went away. Once I let go, the sound returned.

I realize it’s tough to diagnose something you’ve never seen or heard, but has anyone else had this issue? I really don’t want to deal with the dealership telling me either they can’t duplicate or it’s normal. It doesn’t sound normal, but I’ve never had a boosted car.

Thanks in advance for any help or advice.

LT4Greg · 05-03-2021, 07:00 PM

If you could do a video and put it on your thread it might help us determine if something is wrong!�� I do know that my ZL1 sometimes makes strange noises but I attribute it to the supercharger and this is my first supercharged car too. They seem to have different noises than naturally aspirated engines and mine so far has no issues.

Royal Dutch · 05-03-2021, 07:58 PM

sounds like a vacuum leak

Lilwilly · 05-03-2021, 10:17 PM

I’ll try to make a video tomorrow - thanks

Lilwilly · 05-06-2021, 12:06 AM

I haven’t posted videos before so I hope this works. The noise goes away when actuating the bypass valve or after about 10 minutes of warming up.

https://streamable.com/ak39hx

LT4Greg · 05-06-2021, 06:42 AM

Definitely not normal in my opinion as mine surely doesn’t sound like that when warming up the engine. The dealer may have to keep it overnight to check it when it’s stone cold. Could be a loose belt, bad bearing in supercharger or pulley or something else is going on. If the dealership has a good tech you could go and let them see and hear your video clip of the noise to help determine the problem since your ZL1 is under warranty. Good luck and your video was very good on your first posting of a video.��

swisstyphoon · 05-06-2021, 06:55 AM

Quote:

Originally Posted by LT4Greg

Definitely not normal in my opinion as mine surely doesn’t sound like that when warming up the engine. The dealer may have to keep it overnight to check it when it’s stone cold. Could be a loose belt, bad bearing in supercharger or pulley or something else is going on. If the dealership has a good tech you could go and let them see and hear your video clip of the noise to help determine the problem since your ZL1 is under warranty. Good luck and your video was very good on your first posting of a video.��

Sounds like a bad Alternator, or a idler, tensioner bearing.

Lilwilly · 05-06-2021, 10:21 AM

I also thought it was a bad bearing until I manually moved the boost bypass valve and it went away

I like the idea of showing the video to the dealer - thanks!

Lilwilly · 05-06-2021, 11:23 PM

I narrowed the noise down to the supercharger. Talked the the service manager and showed him the video, but as expected he said I just need to bring it in - 3 week wait.

Does anyone have an idea of why the supercharger would make that noise for the first 12-15 minutes of a cold start and then go away?

LT4Greg · 05-07-2021, 06:45 AM

Maybe an internal part of the supercharger, bearing or other part. I would let them replace the supercharger and move on. Major parts have been hard to get since this COVID thing for repairs so that’s the reason he told you 3 weeks. Good luck and let us know when you get yours repaired. ��

hawk02 · 05-07-2021, 07:45 AM

That's the exact same sound my engine made when it had a bad idler pulley. The sound would vary with RPMs.

I've included a photo with an arrow pointing to the pulley that was replaced.

I diagnosed the bad pulley with a 3 ft wooden dowel. Put it right up against the front of the pulley with the engine running and you could hear it buzz when you put your ear up against the dowel. It also vibrated like crazy in your hand. An automotive stethoscope or long screwdriver can also be used to check if the pulley is bad.

I had the pulley replaced under warranty in 2018 and no problems since.

Tyrolblue67 · 05-07-2021, 01:07 PM

I would take a look at the idler pulley as well.
Could be a bad bearing or assembled backwards at the plant causing too much tension when the bolt was torqued down.
Is the silver dust plate just below the bolt on the idler pulley discolored?
Heat from friction could cause the dust plate to turn yellow, blue, green and orange like a rainbow.
Tyrolblue67

CanadianVetZL1 · 05-07-2021, 03:59 PM

Isn’t what you pushed on the bypass valve preload rod?

Lilwilly · 05-07-2021, 06:58 PM

Quote:

Originally Posted by CanadianVetZL1

Isn’t what you pushed on the bypass valve preload rod?

Yes - I actuated the bypass valve to see what it would do and noticed everytime I did the noise went away

05-03-2021, 05:37 PM	#1
Lilwilly Drives: Camaro ZL1, Durango SRT, Mustang GT Join Date: Feb 2021 Location: Palmer Alaska Posts: 16	Strange noise during warm-up I’m reaching out to see if anyone might have had the same issue with their car. I have a 2021 ZL1 that I bought new in February and have been putting the break-in miles on the car. I noticed from day one that I’d get a sound like a low pitched squeal or a idler or belt tension pulled going bad. This would only happen on the first start of the day and last until the car was warm. It varied with engine speed, but went away above approx 1300-1500 RPMs. Today I started trying to find the cause and noticed if I manually move the boost bypass valve, the sound went away. Once I let go, the sound returned. I realize it’s tough to diagnose something you’ve never seen or heard, but has anyone else had this issue? I really don’t want to deal with the dealership telling me either they can’t duplicate or it’s normal. It doesn’t sound normal, but I’ve never had a boosted car. Thanks in advance for any help or advice. __________________ Camaro ZL1, Durango SRT, Mustang GT, Mazda Miata

05-03-2021, 07:00 PM	#2
LT4Greg Drives: 2017 Camaro ZL1 Coupe Join Date: May 2016 Location: Georgia Posts: 5,813	If you could do a video and put it on your thread it might help us determine if something is wrong!�� I do know that my ZL1 sometimes makes strange noises but I attribute it to the supercharger and this is my first supercharged car too. They seem to have different noises than naturally aspirated engines and mine so far has no issues. __________________ ZL1 Coupe, PDR, Exposed carbon fiber hood insert, My Link with Nav, M6 6 speed and Silver Ice Metallic. Mods done: ceramic window tint, GM Accessories Camaro floor mats and Roto-Fab CAI.

05-03-2021, 10:17 PM	#4
Lilwilly Drives: Camaro ZL1, Durango SRT, Mustang GT Join Date: Feb 2021 Location: Palmer Alaska Posts: 16	I’ll try to make a video tomorrow - thanks __________________ Camaro ZL1, Durango SRT, Mustang GT, Mazda Miata

05-06-2021, 12:06 AM	#5
Lilwilly Drives: Camaro ZL1, Durango SRT, Mustang GT Join Date: Feb 2021 Location: Palmer Alaska Posts: 16	I haven’t posted videos before so I hope this works. The noise goes away when actuating the bypass valve or after about 10 minutes of warming up. https://streamable.com/ak39hx __________________ Camaro ZL1, Durango SRT, Mustang GT, Mazda Miata

05-06-2021, 06:42 AM	#6
LT4Greg Drives: 2017 Camaro ZL1 Coupe Join Date: May 2016 Location: Georgia Posts: 5,813	Definitely not normal in my opinion as mine surely doesn’t sound like that when warming up the engine. The dealer may have to keep it overnight to check it when it’s stone cold. Could be a loose belt, bad bearing in supercharger or pulley or something else is going on. If the dealership has a good tech you could go and let them see and hear your video clip of the noise to help determine the problem since your ZL1 is under warranty. Good luck and your video was very good on your first posting of a video.�� __________________ ZL1 Coupe, PDR, Exposed carbon fiber hood insert, My Link with Nav, M6 6 speed and Silver Ice Metallic. Mods done: ceramic window tint, GM Accessories Camaro floor mats and Roto-Fab CAI.

05-03-2021, 07:58 PM	#3
Royal Dutch Drives: 2021 Chevy ZL1 A10 Cpe Shadow Gray Join Date: Mar 2021 Location: New Jersey Posts: 32	sounds like a vacuum leak

05-06-2021, 10:21 AM	#8
Lilwilly Drives: Camaro ZL1, Durango SRT, Mustang GT Join Date: Feb 2021 Location: Palmer Alaska Posts: 16	I also thought it was a bad bearing until I manually moved the boost bypass valve and it went away I like the idea of showing the video to the dealer - thanks! __________________ Camaro ZL1, Durango SRT, Mustang GT, Mazda Miata

05-06-2021, 11:23 PM	#9
Lilwilly Drives: Camaro ZL1, Durango SRT, Mustang GT Join Date: Feb 2021 Location: Palmer Alaska Posts: 16	I narrowed the noise down to the supercharger. Talked the the service manager and showed him the video, but as expected he said I just need to bring it in - 3 week wait. Does anyone have an idea of why the supercharger would make that noise for the first 12-15 minutes of a cold start and then go away? __________________ Camaro ZL1, Durango SRT, Mustang GT, Mazda Miata

05-07-2021, 06:45 AM	#10
LT4Greg Drives: 2017 Camaro ZL1 Coupe Join Date: May 2016 Location: Georgia Posts: 5,813	Maybe an internal part of the supercharger, bearing or other part. I would let them replace the supercharger and move on. Major parts have been hard to get since this COVID thing for repairs so that’s the reason he told you 3 weeks. Good luck and let us know when you get yours repaired. �� __________________ ZL1 Coupe, PDR, Exposed carbon fiber hood insert, My Link with Nav, M6 6 speed and Silver Ice Metallic. Mods done: ceramic window tint, GM Accessories Camaro floor mats and Roto-Fab CAI.

05-07-2021, 07:45 AM	#11
hawk02 Coupe Newbie Drives: 2017 ZL1, 2021 Corvette Convertible Join Date: Jul 2011 Location: Columbus, Ohio Posts: 3,283 View My Garage	That's the exact same sound my engine made when it had a bad idler pulley. The sound would vary with RPMs. I've included a photo with an arrow pointing to the pulley that was replaced. I diagnosed the bad pulley with a 3 ft wooden dowel. Put it right up against the front of the pulley with the engine running and you could hear it buzz when you put your ear up against the dowel. It also vibrated like crazy in your hand. An automotive stethoscope or long screwdriver can also be used to check if the pulley is bad. I had the pulley replaced under warranty in 2018 and no problems since. Attached Images __________________

05-07-2021, 01:07 PM	#12
Tyrolblue67 Drives: 2019 ZL1 Camaro Join Date: Oct 2016 Location: Motor City Posts: 196	I would take a look at the idler pulley as well. Could be a bad bearing or assembled backwards at the plant causing too much tension when the bolt was torqued down. Is the silver dust plate just below the bolt on the idler pulley discolored? Heat from friction could cause the dust plate to turn yellow, blue, green and orange like a rainbow. Tyrolblue67

05-07-2021, 03:59 PM	#13
CanadianVetZL1 Drives: 2021 Chevrolet Camaro ZL1 Join Date: Apr 2021 Location: Nova Scotia Posts: 74 View My Garage	Isn’t what you pushed on the bypass valve preload rod? __________________ 2021 Camaro ZL1 ADM S/C Expansion Tank Dual Aeroforce gauges Eibach Pro Lowering Kit Oracle Side markers (Paint matched) Rear window "wind screen" Xpel Paint Protection Ceramic Pro Coating

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