[miro_ny]

I was wondering if anyone came across this issue. On a cold start it sounds like I have a complete nest of birds under the hood, fades away as the RPM drops after a minute, but still kinda annoying. Checked belts, pulleys, everything looks okay.

You can hear the chirp coming in at around 0:17 and fading out at 0:42 (it's not my car, but another LT4 from a Corvette user with the same issue).

I found a thread on a Corvette forum, they came to the conclusion it could be the high pressure DI system chirping at cold start (they never came to a full conclusion), but I never had this problem earlier. Dealer "couldn't replicate the issue". LOL. Anyone experienced this issue before?

Thanks!

 

[djdonte]

Tough to make it out on a video, I would have to be there, but I listened a few times and it sounds just like belt chirp. If this is a cold start then it fades away when the idle goes back down a bit. Once its settled out play with the gas pedal in park and I bet you can replicate it at a certain RPM. The DI system is more of a clicking noise, almost like valvetrain noise. If you are under warranty perhaps try another dealer? If it only happens briefly (and only on a cold start) its possible by the time he drove it into the shop and popped the hood the noise was gone.

Check your belt and check all pulleys for runout. These belts typically dont show much visual wear. Its possible that its stretched or was contaminated with oil/coolant in the past. You dont say your mileage but if the belt is cheap maybe throw a fresh belt on? It couldnt hurt. Sucks that you only have a 30 second window to detect the noise, if you do it fast, or can replicate it like I described earlier, get a spray bottle a spritz a little water on each pulley to see if the noise goes away.

How to Fix a Squeaky Belt (figure out where the squeak is coming from) - YouTube

 

[miro_ny]

Thanks for the thoughts, it's a 2018 20k miles.

Funny thing is it goes away completely after a cold start, can't replicate the chirping at any RPM later on. I might try to pull the SC belt and see if it still has the sound. Tried the light water spray on the belts, didn't help. Kinda clueless, but I'll keep on investigating.

 

[djdonte]

Thanks for the thoughts, it's a 2018 20k miles.

Funny thing is it goes away completely after a cold start, can't replicate the chirping at any RPM later on. I might try to pull the SC belt and see if it still has the sound. Tried the light water spray on the belts, didn't help. Kinda clueless, but I'll keep on investigating.

I dunno then sorry man. Tough to diagnose over the interwebs. Try a mechanics stethoscope so you can pinpoint the location a little better.

 

[MrSurly]

Exhaust manifold can do this. Check manifold bolts for tightness,

 

[djdonte]

Exhaust manifold can do this. Check manifold bolts for tightness,

Yes an RPM dependent clicking can surely be an exhaust leak but I've never heard the leak go away so fast. Worth a shot though.

 

[miro_ny]

Exhaust manifold can do this. Check manifold bolts for tightness,

So that was my next idea to check if I have a leak. I just wasn't sure if the manifold can make a sound like that. Thanks!

 

[pfram]

Check pulleys. Idle in particular. Replaced mine at 20k for bird chirps

 

[kittyboy]

Sounds like the rear SC bearings, get a stethoscope. If it is, it is not that bad, service the SC oil and see if it goes away.

 

[07GTS]

as its cold u will be fine to remove the belts so only crank is spinning then that will tell u if its belt/pulley related, if it dosnt do it then put blower belt on see if it then does then if so u can see if its belt or blower related, if still not then fit main belt, may help to pin point it

 

[miro_ny]

Great info guys, thanks! I'll check these, starting with the belts to see if it's any pulley/belt related. I'll keep you posted!

 

[Dega Man]

What type of injectors do you have? I have experienced this on several cars with ID injectors which is not a big deal if that is what you are hearing. There are several threads on google search about noisy injectors, which sounds like what you might possibly be experiencing on cold startup. I have a new set of ID 1050X's now that are very noticeable on startup with the hood open especially, the exact same chirp you are hearing. I think this is by there design. Worth checking out.

 

[miro_ny]

Yeah, I still think it's something to do with fuel delivery - either the DI pump or the injectors. Car is bone stock btw.

I'll go ahead and check with HPTuners to see a log and check what happens at the time the noise dies off, even split SOI is an option to check.

 

[Dega Man]

I was thinking that your car was a ported injection engine instead of a direct injection, sorry for posting on the wrong engine.