I did search first, I found some references to engine failures in the early C7s but nothing that seemed like what I'm experiencing.

Hoping someone here knows something.

I have a 2017 GS A8 w/ 2200 miles on it, no mods, no tunes, 100% stock. Proper break-in and 500 mile oil change.

The engine rattles very loudly at 3k RPM.
The rattle begins softly at 1.5k then builds to 3k and is gone by 4k

At 3k its very very loud. If I had to guess, I'd call it piston slap, but does that still happen in modern engines? This loud? Really?

Its not pinging / knocking / pre-detonation, its too loud for that and I'm not feeling any timing getting pulled. This weekend I'll probably hook up my HP Tuners reader and see what it says.

It could be some kind of heat shield or something thats rattling, but why would that be so consistent with a specific RPM.

Any experience anyone can offer is greatly appreciated.

Thanks

EDIT: I put a stethoscope against my engine block to be sure it was coming from the engine and not the transmission or other drivetrain. It's definitely rattling loudest from the driver side of the engine block, though its hard to tell if its coming from the top or bottom. In any case I'm now certain its the engine. The only things I know that behave this way are "Rod Knock" or "Piston Slap" -- either way I had better get a new engine, I don't want some scarred up cylinder wall.

 

Take it in to the dealership....let them diagnose it asap.

 

Couple of issues regarding rattle sounds have been posted.

Some involve the V4 exhaust valves that are in all cars and the two others if you have NPP. These are both motor driven and have levers that actuate buttrtfly valves inside the exhaust. There are reports of those rattling. The V4 partially closes where the NPP valves are open or closed.

Another is the high pressure DI fuel pump and fuel injectors themselves. Both are located under the intake manifold and there is noise insulation in that area. Some have reported it slippping out of place.

Get lots of piston slap in the 8.2 Liter engine in my Street Rod since it has large diameter forged aluminum pistons. But it only lasts a few minutes until the pistons get hot. The LT1 has cast pistons that do not expand and contract like forged aluminum and the cylinder bore is not as large. There should be no rattle even on cold start-up.

If a mechanical engine issue like an undersized piston, rod bearing, high leakdown lifter- plunging a reader into the OBD port will show nothing. Bring it to a dealer.

 

Take it to the dealer!

 

Hope you dealer does better then mine, I have had a rattle, banging from the rear of the car, 18 days now, new torque tube and it's the same and they have no idea where it's coming from. Good luck on your rattle.

 

Has there ever been loose flex plate bolts in the Auto C7s?

OP, can you record the sound somehow?

 

Post up a video to YouTube and then link it here. The fact that it goes away depending on the RPM range of the engine leads me to believe its something loose somewhere and the resonance corresponds with that particular range of RPM.

 

Reminded me another early issue raised with an M7! It has a dual mass flywheel that uses springs between the masses. Some posters had a spring fall out and that rattles loudly!

 

I updated the original post with youtube videos.

Thanks to everyone for the feedback!

I'm really having a hard time accepting that its an engine problem and praying its just a head shield or something.

 

That is not normal. Not to rehash an earlier statement, but have you made an appointment to take it in? Hopefully something is just loose.

 

I may have to but I REALLY don't want to.

In the past, every time I take my car in for some repair, they keep it forever and do a half-assed job.

 

Sounds like you need to find another dealer.

 

Anyone have experience with a bad torque tube? I know people have had issues with them on the C7s. I've seen a few videos on youtube and it seems a bad torque tube will rattle, but I'm wondering if the symptoms are similar to mine. Loud rattling mostly undetectable until 1.5k then worst about 2-3k and gone by 4k.

If I can determine this to be a non-engine issue, I'd feel a lot better about taking it to the dealer. I'm terrified its going to be a connecting rod and they'll end up not replacing the motor and I'll have a scarred LT1.

 

I put a stethoscope against my engine block to be sure it was coming from the engine and not the transmission or other drivetrain. It's definitely rattling loudest from the driver side of the engine block, though its hard to tell if its coming from the top or bottom. In any case I'm now certain its the engine. The only things I know that behave this way are "Rod Knock" or "Piston Slap" -- either way I had better get a new engine, I don't want some scarred up cylinder wall.

 

Flywheel is also on rear of engine, will be interesting to see what is found. Hope it's simple, but agree rod bearing is certainly a possibility.

 

I know what you mean not wanting to take it to a dealer. Nothing but problems every time I go to one. Here is something for you to check out, but yours sounds more like a rattle than a tick.

http://www.corvetteactioncenter.com/...-set-1291.html


On your videos you have the car in track mode. That makes too much exhaust noise. Why not diagnose this with quite exhaust. Here is something else you might like.
http://www.foxvalleymarc.com/Tech_se...ne_noises.html

 

I have my NPP fuse pulled. For me (not via video) its so loud that exhaust doesn't make much difference.

 

I have an appt w/ Abel Chevrolet on Tuesday, 24th. They're the only service shop I'd trust to do it right. We'll see how it goes.

 

What do you think it is, wrist pin?

 

Can't know until we pop it open, but bad rod bearing seems to fit IMO.

I could test it myself if I wanted to pop the heads off but I'd rather just let the dealership deal with it.