Whistles under light throttle

[John Wright]

I have a whistle under light throttle in my factory stock Silverado 3500 with a 6.0L. I've hosed the motor down and there is no change in the sound of the whistle...it only at part throttle tip in, but it drives me nuts. Can these plastic intake be leaking internally and make this sound? It has done this since it was driven off the dealer's lot brand new. It currently has 110K on it and hasn't seemed to hurt anything yet...except my nerves...LOL

[Jim Nilsen]

It is the idle air control doing what it is supposed to do at warm up mode. The in coming air reaches supersonic velocity is what I have been told. It could be tuned out possibly by the right tune. Until Don Bailey was tuning my EFI it would make the same sounds even after warm up when you barely cracked the throttle at any position.

Yes it does make you a bit crazy to hear it because it is totally annoying to hear any whistle. At first I thought it was a belt squealing.

[John Wright]

It does it ALL of the time, not just at warm up. I've asked other people if they hear it and most said "no", but I hear it all of the time, I guess it is because I'm the one manipulating the throttle so I know when to listen for it. I thought that the intake may have a crack inside somewhere, making that whistle...I'm positive that it is internal and not external (gasket seem to be sealing good), and it's not any vac lines loose or split....

[Bryce]

vacuum leak?

I had an intake manifold gasket delaminate and turn into a reed. It was like i was playing a musical instrument. HAHA.

[Randy67]

My Dakota 5.9L whistles at light throttle, no leaks but it has a cone filter so you can hear from inside. I have heard this from carburetors as well.

[77thor]

vacuum leak? . . .

.

+2.

That's my guess, too.

[John Wright]

My Dakota 5.9L whistles at light throttle, no leaks but it has a cone filter so you can hear from inside. I have heard this from carburetors as well.

Mine still has the factory air box, now my 2003 Silverado with the 6.0L was quiet until the dreaded piston slap started at 25K miles....I traded that one off to the dealer and got the 2004 truck that I have now. Just always wondered what the whistle was on this one.

[Jim Nilsen]

My idle air control was doing it even after warmup and it was something that only happened when you just put the pedal down just right and were accelerating.

A vacuum leak stays whistling when the engine catches up but this whistle didn't. That is why I first thought it was a belt slipping.

The IAC could be not just quite right from the very beginning of it's life but still works. May it has something lodged in it that makes it do it?

The owner of the HotRod shop went for a ride with me and said it sounded like a carb whistle and not the belt. it did it with or without the air filter on.

[John Wright]

My idle air control was doing it even after warmup and it was something that only happened when you just put the pedal down just right and were accelerating.

A vacuum leak stays whistling when the engine catches up but this whistle didn't. That is why I first thought it was a belt slipping.

The IAC could be not just quite right from the very beginning of it's life but still works. May it has something lodged in it that makes it do it?

The owner of the HotRod shop went for a ride with me and said it sounded like a carb whistle and not the belt. it did it with or without the air filter on.

One of my buddies keeps after me to fix it...LOL, He thinks it might be killing my gas mileage...heck with 4.10 gearing and it weighing right @ 7,000#...mileage isn't going to be all that great to start with. I'm getting less than 15 mpg right now, but I think the rough treaded BFG MTII's are causing the drop in mileage, not so much the vac leak/whistle...but I could be wrong. I just don't want to spend a bunch of money on it trying to get the whistle out right now...I've lived with it for over 100K now.