[Lilwilly]

Hawk/Tyrol - thanks I will check it out right now.

[Lilwilly]

I checked the idler pulley - it was nice and quiet. I used a long screwdriver on the top of the supercharger and the sound was amplified - actually sounds like it’s coming from the back of the unit, but it’s definitely the supercharger. I let it idle to warm up and a 12 mins I heard a noise like a flap closing and the noise went away.

So basically for the first 12 minutes of a cold start then goes away

[Tyrolblue67]

Originally Posted by Lilwilly

I checked the idler pulley - it was nice and quiet. I used a long screwdriver on the top of the supercharger and the sound was amplified - actually sounds like it’s coming from the back of the unit, but it’s definitely the supercharger. I let it idle to warm up and a 12 mins I heard a noise like a flap closing and the noise went away.

So basically for the first 12 minutes of a cold start then goes away

Glad you checked that box.
Hopefully they'll soon find what's causing the noise.
Good luck,
Tyrolblue67

[Jverado]

Originally Posted by Lilwilly

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.

Mine made a low pitched whirring/groaning noise for less than a minute when cold. I took a video and showed it to the dealership. They replaced both idler pulleys and the supercharger belt.seems fine now.

[Lilwilly]

My service appointment finally arrived today - dealer had it all day and wants to keep it over night. The tech (who seems awesome) said he contacted GM for direction.

I was hoping for a quick fix, but at least they acknowledged it wasn’t normal and seem to be taking appropriate steps to get it resolved.

[Lilwilly]

Dealer called today and said that GM told them to replace the supercharger - they said they need to keep the car and it will take at least 10 days for a new blower to arrive.

[SSallday]

Originally Posted by Lilwilly

Dealer called today and said that GM told them to replace the supercharger - they said they need to keep the car and it will take at least 10 days for a new blower to arrive.

Glad they are going to fix it. Mine was making the same noise as yours, but I brought it in for a different noise. The new supercharger solved the issue completely. The other noise is still there, but I think it's related to the fuel system

[Lilwilly]

Does anyone know if I’ll lose the engine builder’s name plate when they swap the supercharger?

[LT4Greg]

Probably so but mention it to the Service Manager or the Tech working on your car and see if they can remove it so you can keep it.