LS14EVR

iTrader: (3)

I don't mean to freak you out, maybe I heard it wrong. I just can't think of anything besides maybe your cooling fan that would take time to spin down. Was the car already HOT in that video so the fan kicked in?

danbrazda

No, car was a cold start in the video. I need to take a closer look as it spins down. Aftermarket undercrank pulley?

LS14EVR

iTrader: (3)

Do you mean underdrive pulley? Probably not. That should be rigidly attached to crank.

danbrazda

I can't see anything moving under the hood after engine shutdown. What else could be squeaking like that? Check the vid if any of you haven't seen it yet.

RPM WS6

iTrader: (3)

I listened to the vid, here are my thoughts.....

- I don't know what the "Whistle" is, but if it was a vacuum leak it'd have to be a really big one to be that loud, and the idle rpms seem to be too steady for a massive vac leak (unless the car was tuned with that leak). Wonder if it's an accessory pulley/belt system/bearing issue?

- The sewing machine noise sounds about normal for a cammed LS1. Seems to be the expected amount of valvetrain clatter to me, given the mods.

- That squeaking at the very end, after engine shutdown..... I am 99% certain that's your cooling fans. My '00 WS6 made the exact same sound after shut down, and it was the fans. It started after I had a mishap with the trans cooler lines, and blew trans fluid all over the fans. Did it all the time after that.

The on/off fan temps may have been modified to allow fan operation sooner than stock, explaining why they cut on shortly after a cold start. With custom tuning, fans can be set to cut on at nearly any temp. You have to look past the shroud to see the blades moving, a flashlight might help you there. I'm sure that's what this sound is.

danbrazda

Man I really had high hopes that it would be the cooling fans but unfortunately it wasn't. Fans aren't spinning when the squeaky wind-down sound is happening. I don't see anything external spinning while I listen to the sound. It's very hard to pin down where it is coming from. Almost sounds like it is coming from the AC unit down low but the compressor isn't spinning and the AC is off.

The mystery continues. Any input is welcome. Maybe my engine is possessed by a mouse or squirrel that I accidentally ran over.

RPM WS6

iTrader: (3)

Honestly, I can't think of anything else that could possibily make that kind of a noise after the engine is shut off. Nothing else comes to mind, and it sounds exactly like mine did - and mine was in fact from the fans.

Did you look at both fans, and see that neither was moving? I just can't imagine what else it could be.

danbrazda

Neither fan is turning. Does it on cold start/ shutdown as well as hot shutdown. Freakin' bizarre. Might have to put out prize money to solve this puzzler.

Good news is, despite the funky whistles and squeaks, the car run like a raped ape when I want her to as well as a docile daily driver when I need that. 18mpg in town and 27 on the highway. Might have to keep her, noisy bitch that she is.

RPM WS6

iTrader: (3)

Seems like that statement could apply to more than just cars.

LS14EVR

iTrader: (3)

This may be not even be possible but since nothing else seems to be it. Have you tried watching the tensioner pulleys on the AC belt. I don't know how they could keep spinning after shut down, but maybe one is so wasted or something. But I would think it would throw the belt if that was the case. Just throwing this one out grasping at straws. You said you removed the air pump so it's not that spinning. you said both fans are not moving. Did someone add a small cooler that is hidden somewhere with a small fan. LOL. I'll keep thinking about this one.

LS14EVR

iTrader: (3)

Hey, maybe someone put in a forced air fan under your air cleaner to boost positive air flow and hence your good mileage! LMAO!

LS14EVR

iTrader: (3)

ANother long shot. Do our alternators have an internal type fan on them, and if so is there any possible way that could become loose and freewheel so to speak. I've never had a alternator apart so I haven't a clue. Again just another long shot.

RPM WS6

iTrader: (3)

I thought about that as well, with the most likely purpose being an aftermarket trans cooler w/fan, but then I remembered the OP has an M6, which would rule that out. I can't think of any other fluid coolers that would need a fan.

This is an interesting idea. Yes, these alternators do have an internal fan (which is supposed to be controlled by the pulley and thus belt, but if something is broken anything is possibile), and that whirling sound when the engine is still running could also be the result of a pulley related issue. Considering all of the obvious has been checked, it'd probably be a good idea to go ahead and inspect the alternator. It can't hurt, and might knock out two problems at once.

LS14EVR

iTrader: (3)

Maybe a power steering cooler if they got rid of that factory cooler/heater thing. But I think most just put the rad and no fan. Good call on M6. Forgot that part. I'll keep thinking.

jimmyblue

iTrader: (11)

Be sure no genius previous owner installed one of those
"vortex" plates behind the TB. I've seen a truck with one
and it makes a whistley noise. Any sharps in the intake
lineup could.

One pine needle stuck in the radiator could hit fan blades
and make a whine.

Valvetrain will tick, injectors tick but you won't hear
those after a high lift cam goes in. Header primaries
tick. What to worry about is not the sewing machine,
but something that's one out of 8 and louder.

danbrazda

An update to the mystery which points to the AC unit- I crawled under the car to inspect the AC unit from the bottom. The compressor has a bit of play in it and I turned it by hand (only about 1/2 inch). When I started it up and then shut it down there was no squeaky wind down noise. BUT- when I started it up and shut it down right after that the sound was back. Is something still spinning inside the AC unit after shutdown even if the AC is not on?

The AC works perfectly (better than our 20009 Nissan Rogue) but is this some kind of early sign of AC compressor failure?

LS14EVR

iTrader: (3)

I got nothing on the AC. All I know is there is a clutch in there. So when the compressor kicks in the clutch is engaged. I know a lot of vehicles will turn the compressor on when defrost is on even if it's on hot. That's about it. Sorry.

RPM WS6

iTrader: (3)

Simple way to test the A/C possibility; just remove the belt, then run the engine. It's the only accessory that has it's own belt.

danbrazda

But I did confirm that nothing, including the external Ac tensioner, is moving on shutdown. Are you saying that there might be something inside the AC unit that will keep spinning?

RPM WS6

iTrader: (3)

I suppose it's possibile. I'm not an A/C system expert, and I've never stripped down the compressor, so I don't know exactly what the internal construction looks like. But if you seem to think that the noise is coming from that location, it's a simple test to remove the belt. At that point, you will either 100% rule out anything to do with the A/C belt system, or narrow it down to something that's definitely related to the A/C belt system.

Given the info we know so far, that would be my next test if it were my car.