LJB123

My 2023 C8 has 4800 miles on it and has a slight rattle noise when it idles. It started soon after I got it and seems to be more noticeable now. I just brought it to the dealership for my first oil change and they said that the noise was normal and coming from the injectors. I asked to hear one of the other C8s they were working on start up and I did hear the noise, but it was very faint. That car had 11k miles on it. I’ve attached a video of the noise at idle. Can someone please let me know if this is really normal. It’s almost like a background clanking sound. Does it get fainter over time? Thanks in advance.

Mark9

That sounds more like a knock to me than injector noise. Does the noise track rpm?

Ron_Attleboro_MA

Injectors are more of a 'tick' sound.
I am going to guess it is one of the NPP exhaust flapper valves or AFM flapper valve.
Try to determine from where, left-rear, right-rear, or middle-rear(from the back middle).
NPP valves are to the side. I believe the AFM is in the middle, in front of the truck tub.
It could be hoses off the engine, exhaust.

Boy it sucks with service tech's have the same saying for everything, "it's normal"!!!

sTz

The injectors are a more uniformed ticking sound, which this is not. It sounds like a rattle. Perhaps a loose heat shield on the exhaust. Sadly, the dealer doesn’t want to deal w/it. Maybe you’ll have better luck at another dealer.

LJB123

Thanks. hear it from all around the car.

LJB123

I don’t think the sound is audible when it’s revved, but I’ll have to try it. I have the NPP exhaust turned all the way up so it probably drowns it out.

Mark9

put the car in stealth mode and see if that changes the noise.

22c8z51

Can you open the hatch and record a video of it while walking around the back of the car?

LJB123

I put it in stealth engine sound and the noise is the same, but it’s easier to hear in this mode. Also, I revved it a little and the noise is still audible, but doesn’t seem as loud with it revved slightly (but that may be because of the louder rpm sound).

LJB123

Attached is another video with hatch open and in stealth mode walking around the back of the car. Thoughts?

BPHORSEGUY

As said above injector noise is ticking not ratling ?

Andybump

What I hear is a random knock - like rattle - a component that occasionally bumps another component. Since you verified that it happens in stealth as well as when the valves are open - I think that rules out a rattling of those valves - plus the noise from them - if there is any - is a higher pitch rattle. This sounds like something heavier.

Mark9

If you can, get a long extension or screw driver and put it against the exhaust and put on your ear. See if it is more pronounced. Have someone run the engine up and down. Both sides. See if it’s more pronounced on one side or the other. If it doesn’t track rpm it’s probable not a rod or bearing knock. Which is what you don’t want to have. Do the same on each valve cover.

LJB123

The rattle doesn’t seem to change the pitch.

Mark9

If it’s random which it sounds like I don’t think it’s engine internal related. Annoying for sure. Can you hear it inside the cabin?

Mike's LS3

Sounds like a knocking noise as if something is rubbing against another object.
Rev the engine slowly and listen whether it speeds up.
Close NPP to quiet the exhaust and pinpoint where the noise is coming from.
Put your foot on the tail pipe and try to move it, possible exhaust hanger rattle.
Buy a stethoscope for autos and poke around with it.
Take it to another dealer.

LJB123

It doesn’t speed up when revved. Yes, I can hear it while I n the cabin with top/windows down.

SMOKN C8

Mine has something similar and im just over 5000 miles.

Ill ask the dealer about it one day but dont care enough to make a special trip. If it is something bad, it will eventually get worse and its all under warranty either way. It has not changed since i first noticed it. It

DrewK769

I think that is just the transmission rattling a bit. When the car is in gear and under any load, does the sound disappear? Performance manual transmissions often make noise when not under load.

Waterline

I keep one or two in my shop.
https://www.harborfreight.com/mechan...ope-63691.html