Squealing noise silverado 2014 when she is shut down

[Rush78]

I have a 2014 1500 silverado 5.3. When the truck is off there was been a squealing noise coming from under the hood, it's there for a long time after too. Say 5 hours later or more. It will make the noise and stop then do it again. Kind of reminds me of the old dial up modems. I have never heard it in any of my older trucks and have no idea what it is. My truck is about a year old and has less then 12000 on it. Was wondering if this is normal with the new models and what it is. The first time i ever heard it was right after the annual inspection. I took her home and gave her a wash and wax. Never thought much of it at the time because i had just gotten her back and figured if it was something wrong that they would have picked up on it. Any help would be appreciated, even to kill my own curiosity now.

[Jsdirt]

GM ... I really hope you guys watch this one. WTF are you guys doing over there???

 

 

Wow is that odd! Trapped aliens in the valve covers!

 

It definitely sounds louder on the passenger side. Almost sounded like it was coming from the alternator. My theory is it's either that or the ignition coils, getting a voltage command from the computer that shouldn't be there with the key off. Wow is that strange!!

 

Gotta love modern vehicles!

[Rush78]

I have no idea how the evap works. So i am out to lunch on the hole thing. It sounded good and made sense to me, i wouldn't know if it's fit to eat. This is where you are suppose to trust the dealer to tell you what's wrong and what's normal, but a lot of times it leaves you scratching your head. I did have an older mechanic say something to the same extent having to do with the fuel line and a valve.

I am not going to stop until i get a definite answer to it and the next inspection i am putting it down as a complaint and having it checked again, unless something comes out on writing.

[Rush78]

By the way thanks for all the feed back. After learning a lot and getting some good ideas for the problem. I am not a mechanic but find this stuff interesting.

[Rush78]

I stopped by and they said as long as there is nothing lighting up, the truck is doing what it's supposed to be doing. The first time i noticed it she just came from an inspection, if there was anything out if wack i would think they would have picked up on it. That being said she is fully covered by warranty. So if i do notice something going wrong (loss of power, A/C, etc) i ll be bringing it in right away. Other than that they told me it would be a waste if it's not going to happen while there, because it would be impossible to trace without the noise.

When she goes back fir a semi annual I am going to be asking them to look into it again even if it's not happening.

There's no smell from the A/C and nothing appears to be leaking.

I have forwarded on the second video and asked exactly where the relief valve is that they are taking about. But i haven't heard back. I get off work Monday morning so I am thinking of swinging in on the way home to see if there is anything new they might have in it.

If it is the PCV valve causing this, shouldn't it be running for it to be making the noise? From what I understand it's creates a vacuum which when running you should hear a difference. This noise happens hours later, I have never heard it it immediately after i have shut the truck off from driving. With the exception of the other day when I heard it and it went, i started the truck for a second and shut it down. Noise was back. Please correct me if I am wrong, don't know much on it.

[tbarn]

Get a length of garden/heater hose and use it like a stethoscope next time it does it.

[The Zip]

If it is the PCV valve causing this, shouldn't it be running for it to be making the noise? From what I understand it's creates a vacuum which when running you should hear a difference. This noise happens hours later, I have never heard it it immediately after i have shut the truck off from driving. With the exception of the other day when I heard it and it went, i started the truck for a second and shut it down. Noise was back. Please correct me if I am wrong, don't know much on it.

 

The short of the PCV valve, handles venting pressure into the atmosphere. It doesn't run, just a static component. A failed PCV valve can cause noise in the form of a whistle or whine. Don't know if you can find the PCV valve but the easiest way to see if it's the problem is to temporarily block the vacuum source to the PCV valve and see if the noise changes or goes away.

[The Zip]

Heard it, I wouldn't be comfortable with that sound. Since you first noticed this after your annual inspection, it's fair to say the sound may be connected to something they did or didn't do. Was this a state DMV inspection or just one of your annual inspections at a local garage? What type of service was done for this annual inspection? I agree with Jsdirt, electrical. So, disconnect your battery for about 10 minutes or so (no logic for 10 minutes) and see if that resets something. One other thing, how old is you battery?

[Jsdirt]

The idea of the PVC not working correctly is that there could be unburned fumes venting from the crank case. This could also cause the oil to go dirty or sluggish, from what i read somewhere.

 

I've got a '00 4.3 in a '89 S10 Blazer with no PCV system at all - oil stays nice and clean, FWIW.

 

 

 

...

 

With normal operating components I would agree, but Rush has some component that has failed or is failing and the pressure is not venting correctly.

The pressure would bleed past the rings, and on the cylinders with open valves, into the intake by the time you got out of the truck after shutting it down. Highly doubt it's the PCV system causing the sound based on that fact.

[The Zip]

Get a length of garden/heater hose and use it like a stethoscope next time it does it.

Don't know if that matters now, dealer says he found the issue when he...

 

 

...traced the noise and found it coming from a relief valve belonging to the evap system, which is located under the hood in that area.

[The Zip]

I stopped by and they said as long as there is nothing lighting up, the truck is doing what it's supposed to be doing. The first time i noticed it she just came from an inspection, if there was anything out if wack i would think they would have picked up on it.

 

Regardless if a light is on or not, there is some air audibly venting. Normal for a vehicle to vent, but to hear it there must be a defect somewhere with either the component or a piece supporting the component such as an O ring or grommet (using the PCV valve as an example, may be something else). Go to an auto parts store and ask the tech to show you where the PCV valve is located, spend about 6 bucks and change it out. This might fix your problem versus waiting for a light to come on.

[Rush78]

I was thinking electrical forsure. She was inspected at Hickmans Motors for her first annual. I am not sure on the date on the battery, have to check that one when i get a chance. I am assuming sence the truck is not even a year old it can't be to old itself. She has all her warranty so I ll take her back to the dealer and see if they can explain it going on. The only problem is that it might happen and it might not. Don't always hear it and you have to be listening where she is not as load with the hood closed.

[Jsdirt]

Can't be the PCV. Once you shut the engine down, the vacuum or pressure there stops.

[The Zip]

Read somewhere it may be a bad PCV O ring. Pull the PCV and see if the O ring is hard and brittle, if so, replace with a new ring. If not, this wasn't a costly investment, the ring should only be a hundred or so pennies.

[jimlem]

Everything above sounds well thought out and researched. But here we are again with one of GM's weirdest issues yet and they are still claiming it's normal. All based on some old timer mechanic who might have heard it before. As stated above this cannot be normal as the system is sealed and nothing should be venting and thereby causing such a noise. I have one other rather odd thing you can easily check. I know my TS skills are not up there with most of these guys but I'll be damned if it does not sound a bit like a horn receiving just enough voltage to to activate at a low volume. It even has slightly changing tones or notes. Can you try pulling one or two horn wires (if there are still two horns used) when the sound is activated? If nothing else, pull the negative battery cable during the sound and see what it does. If anything at all changes then you know they're just B.S.ing you like everyone else because if it's a pressure release of the evap system then battery voltage should have no effect. Just be sure before you talk yourself into believing their liar's club. Good luck.

Jim

[Jsdirt]

..... the ring should only be a hundred or so pennies.

 

As long as you don't buy it at any GM dealership ...

 

I bet that o-ring is $35 over there ...