rmorin1249

I noticed this morning for the first time a fairly loud knocking sound when I started my C7. Temp was about 35 degrees F. Low was about 32 last night. I did not notice this noise last winter even when the temps were in the teens. It goes away after the car is driven for about 10 minutes. It does not sound like injectors or lifters. It is more of a rattle than a knock but is quite noticeable. Any ideas? I don't relish taking it in the the stealer but I should document it in case it is an internal engine issue.

DALE#3

If you have to take it to the dealer for documentation.Take it their for them to figure it out.That is why you pay big bucks for a car with a warranty.
Easy first.If Engine? Oil level,oil pressure idle,then rev.
Gonna be hard to judge a noise from a keyboard.A rattle is usually something loose.Could be exhaust rubbing hitting?
Could be something in your backing plates around brake disc's.Could be...Alot of tings

LT4CMG

What Dale said. Reading your signature, doesn't sound like you have the dry sump Z51, which has some odd sounds if you're not used to dry sumps, but diagnosing it on a forum will be difficult. Could be as bad as the dreaded rod knock, or something completely inconsequential. Sorry about not being able to help more, but get it documented for sure

rmorin1249

I will definitely take it in. Last oil change in March with Mobil 1. Down to 25% on DIC. Will change in a couple weeks. Oil pressure at idle is 30 psi. Not a dry sump. Took another drive a few minutes ago and no noise. Car drove like a dream.

DALE#3

When was the last time driven before you restarted and heard the noise?
More time less oil around crucial internal parts.Then add 30 degrees.

I would document it with dealer for sure.You could be trying to listen for something when it's normal at Cold Start.Engines are nosier the colder it is.
Good thing i noticed with this engine it doesn't go to a real high rpm at start up.That is huge for the long run

Kevin A Jones

Take a video and post it here, most likely the audio will be enough to identify the issue or hopefully the lack of an issue.
Does the sound seem to be coming from a particular part of the engine?

rmorin1249

I'll give it a try tomorrow morning.

Red C8 of Jax

When they put your car back together after the TC replacement, they could have NOT attached your muffler correctly. When its cold it rattles and when it warms up it stops.

NSC5

I agree with Red C6 that this is likely a loose part of the exhaust or another attached point that is making a lot of noise until it gets hot and expands to overcome the attachment looseness.

rmorin1249

I'll definitely have my dealer check this out but the noise sounds like it's coming from under the hood. I'm going to drop it off one evening next week so it can sit overnight for a cold start.

Rebel Yell

Good luck Randall, I hope it's nothing serious. But, if it is it may be time for that new Z06.