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Discussion Starter · #1 ·
Yesterday was the second time I've heard a strange alert/noise coming from beneath the hood about 30 minutes after being backed into the garage and parked/stopped. I was able to capture the sound, but of course I only had a partially working cellphone on me whose A/V recording is somewhat lackluster and sporadic. Any ideas what it could be? Has anyone else ever heard this sound?

If it happens again, I'll take how ever long it takes to grab my good cellphone, and this time I'll keep the phone in certain areas for maybe 10-20 seconds at a time as I probe around for where the noise is the most intense. It's barely audible from inside the car, and most noticable looking under the hood, around the front-passenger area. I mentioned this noise in someone else's thread on November 2, 2021, but it was unrelated to what the OP's noise was.


Anyway...here's the noise...
 
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That is weird. You might be able to pinpoint the noise a bit better using a 3' length of garden hose as a stethoscope maybe? I know my wife's Subaru has an electric motor that comes on a few hours after it's been run to manage the evap system. (Odd to walk into the garage to hear it running.)
 

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Discussion Starter · #3 · (Edited)
Until replaying that YT clip in the car this morning, I didn't realize how persistent the noise was. I thought the noise had gone away for longer periods, but cranking the volume really allowed me to hear it more regularly. In watching the video, I think it was loudest around the top of the alternator. I wonder if the voltage regulator or some other electronic component is causing it. It does sound as if some alarm/alert is sounding, like a CMOS battery is low. Or, perhaps the system randomly performs some kind of self-diagnostic thing after the car's at rest for a certain period of time, and that's the sound it makes during testing.

That noise hasn't returned, but this morning two new noises accompanied by racing/wandering RPMs started happening after about 20 minutes of driving. After going through the drive-thru and barely accelerating, a ghostly/windy "WOOOooooOOOOoooooOOOoooooooooooo.............." was coming from the front driver-side, but the good cellphone didn't pick up the sound. That sound was accompanied by the RPMs suddenly wandering around with just a tiny, quick depress and release of the gas pedal (while in P). The RPMs would shoot to 3000, then remain elevated long after the gas pedal was released, and the RPMs would loosely wind down as the needle bounced around a little. It's never done either of those things. The RPMs and engine always sounded and felt tight, and the RPMs would quickly return to idle-speed without any needle craziness. After goosing the engine above 4000, the ghostly noise stopped, but the needle wandering continued. After turning off the engine it sounded like wind was lightly blowing through the front interior of the dash as a faint, leaky/fizzing noise came from the driver-front area, and I could also hear it faintly while looking under the hood. It stopped and never returned.

Gremlins in the system at 60,000mi. I'll probably have the charging system tested to make sure that''s okay. The car drives fine and there are no leaks or smells. First thing I'll do is disconnect the NEG battery terminal for a minute and see what that does.
 

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Bearing noise in a tensioner or some rotating assembly?
 

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Discussion Starter · #5 ·
On playback on my computer, I can hear the ghostly noise, so I've uploaded the footage from this morning's haunting, The sound seems to mainly emanate from the left speaker, and I'll note just above the clip at what times the sound is starting, just so you know what I'm talking about. It phases in and out, or starts loud and slowy graduates down in tone. At first, I couldn't hear it because I was focused too much on the engine noise. You may have to turn up the volume to hear it... I noticed it sounds clearer when I played the clip via Potplayer or VLC. It's possible Youtube's processing degrades the audio.

I can start to hear it around :48, then it tapers off. Then again at :59. Then 1:20. I realize now I should've talked less, but I can still hear the noise in the background as I talk.
 

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Discussion Starter · #6 ·
Just out of curiosity, I decided to check if the Apple Airtag makes any sounds if the battery starts to die. I didn't find anything related to that, but I did find it does make some sounds that are kind of similar to what I'm hearing under the hood...but not really. What's interesting is, around the time I first heard that noise back in November 2021, I felt I had been "observed" by a shady individual while parked at a Walmart. When I came out of the store and started my car, a distinct car with a young, bearded guy (who looked kind of gang-like) started driving by my frontend slowly, then he nearly stopped and appeared to be looking down at my license plate and mouthing the characters. He then drove away, then drove by a second time, and did the same thing, then he parked three spaces away from me and I decided to leave. When I returned home three hours later, I played my home surveillence footage around the time I saw that creepy guy in the car, and to my surprise that security footage revealed someone showed up at my home about ten minutes after that encounter at Walmart. A fully tattted, muscle-bound, thug-like guy with a beard parked his vehicle out-of-sight at the end of my driveway, and he wandered around my property for about two minutes. Unfortunately, the heavy foliage around my side yard prevented me from seeing what the guy was doing. Long to short, I asked around, called the city, utilities company, etc., and that guy wasn't there for any reason related to anything normal. I gave the footage to the police, and I did my own gumshoe work and found out that guy had rented a crappy house two months prior that's located about five miles away from my home. Long story... Some investigative work determined that guy is in no way related to construction, home inspections, real estate dealings, land surveying, gas leak detection, or with DES or the EPA, etc, etc. He had no reason to be on my property. The guy at Walmart seeming to read my plate, combined with this odd guy showing up at my home around the same time, had me thinking that someone ran my car's tag, determined I wasn't home, and gave the word for someone to go to that property to access it while I was away. Point being, maybe my car has some tracking device installed, and it makes that noise when someone's trying to ping or locate it.

 

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Discussion Starter · #8 ·
do you only have the sound if the engine's running? how about if car is set to acc or on but the engine's off?
The first noise I posted about (in the engine compartment) sounded when the car had been parked/off for at least 30 minutes. When it happened for the first time in Nov/2021 (after being parked in the garage for 30 minutes) the act of pushing the ignition button once for ACC quieted the sound and it never returned until yesterday.

The second sound (ghostly/windy) that I posted about was when the car was in D and I was creeping through the drive-thru, and then persisted as I proceeded to my destination. Once parked, it was making the noise (and the odd-RPM fluctuations were happening) in P and N.

The third sound was like a slow balloon leak or windy fizzing noise that was noticable after turning off the engine and powering down. It lasted about two minutes and then vanished. Never heard that sound before this morning. Almost sounded like wet air being forced through a restricted opening at an inconsistent rate.
 

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As I said in my first reply, my surprise noise with our Subaru was an evap emissions pump. It sure sounds like balloon leaks or fizzing noises could be coming from a pressurized fuel system if you are not obviously losing refrigerant or coolant.

I know that the sound of an A/C system equalizing after turning a car off can be weird also; I've heard that in numerous cars.

Again, if you have the noise happening in your presence, use a 3' piece of hose and locate it.
 

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Discussion Starter · #11 ·
The following day, everything was again normal and sounds the way it has since buying the car. The following morning, after driving roughly the same route, I parked and depressed/released the gas pedal slightly and quickly, and the RPMs barely got above 1200 and the needle came down smoothly and instantly. The reaction of the engine to the small depression of the gas pedal I applied was consistent with how it should be, whereas the previous morning the RPMs were out of control and the engine/throttle body was reacting like I has was depressing the gas pedal halfway, and then upon the deceleration phase it was as if it didn't know what to do, so the tach needle stayed elevated at around the 2000 +- range and then gradually floated down tentatively.

Upon video reflection, the one thing I noticed wasn't happening the previous day was that at the end of deceleration phase (when the RPMs return to idle) the hollow-sounding, low-noted "whoomph" wasn't present. That noise almost seems like pressure being released somewhere. I believe I mentioned that noise within the first few months of owning this car, and I later just assumed it was normal. Since that sound was absent on that morning, I wonder if an elecfronics glitch prevented something (perhaps the EVAP system) from behaving the way it normally does, and eventually the act of goosing the gas and restarting the engine a few times corrected the problem.

Yes, I got pictures/video of both vehicles, both guys, both license plates, the rented house address and management company, etc., and told the police to keep that information on file in case something ever happens to me and my family, such as a home invasion or whatnot. Following that incident, I installed another camera system with many motion/human body detection-equipped PTZ cams around the house and in the wooded areas to focus on the house to show what's happening. I installed multiple layers of motion sensors around the property that set off audible alerts inside the house. No one's able to access any point of my property without being recorded as cameras track their movement and alert me to what's happening, and the A/V footage is stored locally and remotely in multiple places to better ensure the footage is there if something criminal ever happens.
 

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Weird stuff. It it ever starts making weird noises again, go pull off the gas cap to test the evap system theory.
 

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Discussion Starter · #13 ·
The below video is from the day after the RPM issue, where things were normal again. They were actually normal later that morning when it first happened. I realize my account of mileage ane RPM readouts in the attached video aren't very accurate. Getting over an extreme head cold and w/Sudefed that's making my head spin and having me talk faster than usual, so my recollection is kind of messed up. Looks like the first part of my first video (where things were wrong) had the RPMs hovering slowly below 2000, and after I restarted the engine and goosed the gas to about 4000 RPMs, the quick touch/release of the gas pedal had the RPMs float to near 3000 and remain there briefly before the needle staggered down to normal again. But I can't seem to capture that "Whoomph" sound. It's too bassy and faint. When I tried to record it in May 2021 beneath the car, it sounded like a high-pitched "chiiiink!" The timing of that "chiiink" noise under the car coincides with the "Whoomph" heard from inside the car.


 

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Discussion Starter · #15 · (Edited)
As I was exiting the garage to do some yardwork, that alert thing under the hood started again, so I ran to get my good cellphone, and once recording the alert//noise persisted for about two minutes, then went silent for good. So I'd say it was sounding for about three minutes that I was able to detect. I listened more carefully and placed a finger lightly on various components to see if I could feel a vibration and alter the sound. Placing a finger on the housing of the forward VVTSV (true front of engine, right side - near the alternator) seemed to alter the vibrations of the chirp, making if more muffled.

I'll have to look at it more closely later, because in looking at the attached pics the portion of the housing where the electrical connector snaps on appears black and burned, like a short happened, or it could be leaking oil. It could just be a black factory marking, since nearly every connected piece on the car, from suspension to hoses to electrical connectors) has a unique colored marking/dot where the piece mates to or terminates. The sound can also be heard nicely beneath the car, roughly between the oil pan and CVT pan. Perhaps the CVT valve body is creating an alert to indicate something isn't quite right. Will update if I find out anything new. I set up a PTZ cam near the front of my car so I can hear if the alert sounds again while in the house. I just cranked the volume on my security cam TV to make sure I'd hear it when/if it happens again.

UPDATE: That VVT isn't burnt or anything. Once I was able to zoom in with better lighting, I could see nothing wrong from the outside (refer to pics 6 and 7). Not sure if a defective O-ring within that valve could cause that kind of electronic-sounding noise as pressure escapes without allowing any oil to escape.
 

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I'd go to a dealer, and walk in and talk to the shop manager and ask what could make that noise. No don't let them have the car unless its under a warranty or you want to. It would be interesting to know what it is.
 

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Discussion Starter · #18 ·
I'd go to a dealer, and walk in and talk to the shop manager and ask what could make that noise. No don't let them have the car unless its under a warranty or you want to. It would be interesting to know what it is.
Yeah, I might do that at some point.

I had a thought about what it could be, based on the timing. Perhaps there's an alert reminder when the CVT fluid hasn't been changed every 30,000 miles. Around the time of the first alert back in Nov 2021, I was (I believe) at or just beyond 30,000 miles. Heard it once and never heard again until the following year around 60,000 miles. Others here with a 2021-2022 would have to have not serviced their CVT at the 30,000 to help me determine if that alert happens. I suspect that if it's related to CVT fluid, then once it's changed and the deterioration count is reset, that might be the catalyst for the "alert" to reset to 0 and then only happen again in another 30,000 miles. Since I haven't changed my CVT fluid yet because it still looks good with no metal anywhere, it's at least possible those alerts are somehow connected to that lack of Nissan-specified service interval. It hasn't alerted again. Perhaps it only alerts from time to time within a certain mileage range, say from 30,000 to 30,500, after which it silences.
 

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With automotive lube oils its the additive package that "wears" out, you won't see metal from that. Remember the fluid, especially for a CVT is an integral part of the transmission, it is just as important as any other part inside that aluminum box. Why play a costly game? Go to a casino and put a few hundred down that is a cheaper gamble than your transmission, and with that you have a chance to win something, gambling with your transmission is a lose, lose game with zero winnings.
 

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Newbie 2020 owner here but I've experienced strange sounds from the left speaker(s) too. It was my CarPlay and FM radio somehow both operating at the same time with FM about 97% of the sound and CP at, like, 3%.

My Mazda 5 makes "weird" sounds for about :15 secs after shutdown from the throttle body circuit which is right up front next to the radiator so very easy to pinpoint.

FWIW
 
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