[Ashleyk]

High pitched whistle noise, almost sounds like pressure or radio interference. But I know it’s not interference since it was present when radio disconnected. When I turn off the engine it’ll last for a few seconds. I left a link with video… Log into Facebook
It’s a 93 s10 4.3L
I think it has to do with AC but not really sureYouTube link

 

[Rhotpursuit]

You should post the video on YouTube, then provide a link.

 

[Hoosier Rick]

My 1992 4.3 devoloped a whistle. The cause was a bad TBI base gasket.

 

[MyWorkInProgress]

Vacuum leak probably, does it come from the hvac control area?

 

[Big Buford]

Listened to the video but hard to tell much. It would be helpful if you could describe conditions/situations that generate this sound. Happens all the time? Only when using AC? Only when ignition ON? Need a little more info......

 

[Innate]

Vacuum leak probably, does it come from the hvac control area?

Vaccum in HVAC is always a hiss for me, heard that plenty of times. Or maybe fuel pump related noise. I have a chinese fuel pump currently that is noisier than it should be, no problem with it other than having to ignore the noise, on my winter beater whose life will be over this June, so just living with it. I assume it is not a fuel system leak, as there is no fuel escaping and it runs fabulous.

 

[Ashleyk]

You should post the video on YouTube, then provide a link.

You should post the video on YouTube, then provide a link.

ok all set video uploaded

 

[Ashleyk]

Listened to the video but hard to tell much. It would be helpful if you could describe conditions/situations that generate this sound. Happens all the time? Only when using AC? Only when ignition ON? Need a little more info......

The sound is present always when the engine is running. You can only really hear it from inside the truck. The AC can be on or off… when you turn car off the hiss will remain for a few seconds. Also when you step on the gas it gets louder.

 

[Ashleyk]

Vaccum in HVAC is always a hiss for me, heard that plenty of times. Or maybe fuel pump related noise. I have a chinese fuel pump currently that is noisier than it should be, no problem with it other than having to ignore the noise, on my winter beater whose life will be over this June, so just living with it. I assume it is not a fuel system leak, as there is no fuel escaping and it runs fabulous.

She’s running good, and I don’t notice any fuel issues, however when you accelerate the noise dose get louder.

 

[Ashleyk]

Vacuum leak probably, does it come from the hvac control area?

I can’t identify where exactly yet

 

[Rhotpursuit]

I can't hear any whistle..

 

[Innate]

I'll put $20 on it being vacuum, any takers? I can hear my fuel pump from the outside, and it doesn't change with engine speed, which a fuel pump noise shouldn't. What happens to the noise if you pull/open up a vacuum line into the cabin while the engine is running?

 

[Big Buford]

Vacuum leak....probably under the dash...you could test for that by using some sort of clamp on the vacuum hose in the engine bay....the one that goes through the firewall ending under the dash. When engine running and that vacuum hose clamped, if the noise goes quiet, then you have found the leak.....

 

[aitch]

I listened to the video twice and didn't hear anything odd. The noise description has evolved from a whistle to a hiss. Given that, plus the symptoms listed in post #8, I'd suspect a vacuum leak somewhere in the HVAC controls.

 

[420blazer03]

Could be alternator bearing, check under the hood

 

[Innate]

Could be alternator bearing, check under the hood

Good thought. If you don't have a mechanic's stethoscope, get the longest handle screwdriver you can and put your ear to the end of the handle, the tip onto what you want to listen to. Be careful moving it around the pulleys while running, and I assume you have read the operators manual for the tool. By comparing the noise in various locations you can make a good conclusion. Be aware that alternators are always noisy to some degree if you are listening that way, so look for a noise like you've been questioning.

 

[needawheel]

with your drivers door open, turn the key on without starting the motor... does it make the sound when you do this?

 

[needawheel]

I can't hear any whistle..

i believe in the video the noise in question sounds like background noise and is present from start to finish.
fuel pump, vac leak, alt are all good guesses... ill throw in belts/pulleys for good measure.
she just needs it narrowed down now.
"When I turn off the engine it’ll last for a few seconds" would lean me towards fuel pump and/or hoosier rick's post above...

 

[Hankwesty]

I had a whistle in my 2003 Z5, oil level was way low and after oil change it went away.