Squealing noise silverado 2014 when she is shut down

[Rush78]

I have gotten an answer from Hickman motors which actually makes a lot of sense to me.

The video has gotten around the rest of the garage and was seen by one of there mechanics who has the exact problem. He has 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 fuel system in the new trucks is a fully inclosed pressurized system, everyone knows what happens to gas in a cherry can left in the heat, the valve allows this pressure to vent. Which explains why the first time I heard it was when I gotten the truck back.

That day was the first extremely hot day we actually had for the summer(I live in Newfoundland, Canada). I had just filled the truck up and was washing/waxing it before we left to go camping. I also live in a very quiet neighborhood which makes it the perfect time and place to hear it. After thinking back all the times i heard the noise the temperature and quite had played a key roles. Even with the latest time where the temperature and humidity were high.

So the truck is actually doing what it is supposed to do. Plus the sound When you think about it and listen to it again actually sounds like a small toy train whistle. It happens later after the truck has been sitting for a while because the pressure is relived normally with the engine running and and gas flowing. While she sits the pressure builds.

Not sure if I explained it good enough for anyone to make any sense out of it. But we got talking about it with the Hickman motors guys and it made plenty to me and them.

I also checked my battery, which is all good, and disconnected it to see if it helps.

I got another full tank of fuel today so all i need now is a hot day. Which doesn't look good anytime this week....lol

The video is still being sent to GM from what I have been told.

[Jsdirt]

That EVAP system is supposed to keep the fumes in the tank, so by design it shouldn't be venting pressure to the air at all. It's supposed to draw it in the engine on start up - the computer controls the little valves that send it to the intake. If you have a leak like that, it usually throws the light on. Makes sense that pressure venting would make that sound - I've heard a SLA battery do that when a failed regulator sent out 19-21 volts. Cooked the thing alive. Could smell rotten eggs and hear the whistle of the saftey valve venting pressure.

 

Stupid EVAP system shouldn't be in vehicles to begin with, but that's another topic for another day!

 

It's the most ingeniously engineered system for vacuuming hundreds of dollars out of your wallet. I think it was designed solely for that purpose ...

[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.

[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

[Rush78]

Lol...the old time mechanic was a Captain of mine at work. He doesn't work with GM. He said that there is a valve or something there that he believes they use to check the fuel pressure and possibly they never tighten it or something when they did the inspection. Now this was years ago, he's not up on the new models with the in closed system. I asked Hickmans what they do to check the fuel pressure and stuff lime that when during an annual inspection and they said all they do is hook it up to the computer. If there was a problem it would show up there or on your dash. Nothing showed up and nothing on the dash. Truck runs perfect lots of power and get up.

I have thought about and going to doing what you said and pulling the negative when i hear the noise again. Like you said that takes the electrical out of the question all together then if it still continues. Now i just have to wait for it to happen again, who knows when that will be.

[Rush78]

Hopefully this video does make it to GM and they actually do come out with an official statement on the problem, weather it is a recall or what. I am interested to see what the head office is actually going to say. Until then my truck is covered under warranty for 160 000 i got a lot of going for something to happen, i am lucky if i put 15 000 on her a year.

If and when it do happen again i ll take another video pulling off the negative cable that way i can post it and got something else to go back with if it does stop.

[Jsdirt]

Just FYI - the EVAP system has no bearing on how well the truck does, or does not run. It's a "feel good" system designed to keep treehuggers happy - nothing more. Somehow gas fumes are to blame for all the world's ills. It could just be the fact that they screw all of us by diluting the fuel with ethanol, and so you need a sealed system in order for the fuel to not go stale in 3 days ...

 

EVAP started in '96 with OBD-II emissions systems. It was there before that in the form of charcoal canisters, but you could easily disconnect those and throw 'em in the trash without failing inspection due to a "check engine" light. Now if there's a tiny little leak, it throws the light ... and in communist states like mine, you fail inspection, and if your not mechanically inclined your forced to shell out HUNDREDS of dollars in repairs.

[Rush78]

The car charcoal canister was what my captain was telling me about on the old rigs. On my 07 Silverado the evap code was always coming on. Got to the point where i didn't care about the engine ligjt as long as the truck still ran and it was blinking....Lol as the old saying went around here Ford was always found on road dead and the chev kept going but was lighting up like a Xmas tree.

[tbarn]

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

[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.

[Rush78]

Ok. So here is a undate on the Squealing noise. I finally got to hear it again and this time i disconnect the battery cable. The result was no different, even with no power from the battery you can still hear the noise. I did so more poking around and it sounded to me like it was coming from the alternator area, at one point to me it actually sounded like the alternator.

Now Like i mentioned before i don't know much on the whole evap system but could it be a purge value sylenoid making that noise? I am not sure where it is too on this truck. But could that be what the Hickman mechanic was talking about.

I have another video but having trouble uploading it.

[Rush78]

Here is the new video.

Watch "2014 Silverado Squealing noise!" on YouTube

 

[Jsdirt]

Battery disconnected eliminates an electrical cause. Has to be pressure venting from EVAP. I have no idea where those components are located on the new ones.

[GLSierra13]

Could it be coming from the A/C compressor or an A/C line somehow? I know next to nothing about A/C but the compressor is in that same area. Is it somehow bleeding off excess pressure?????