Loud intake whistling problem

[jbai322]

Alright, I have searched this issue and found good information pertaining to the TB whistling problem, but I do not think that is my issue. I believe the whistle is coming for somewhere else around the intake system. Here's my problem:

On a cold engine, there will be no whistle what so ever. It is only until the engine warms up a little that it spontaneously just starts to whistle very loudly. This whistling only happens at idle or very little throttle. The whistle is so loud that you can hear it from about a block away, and my car is also running straight pipes. So you kind of get the idea of how embarrassing it is to drive around with this problem.
Another thing is that once I turn the engine off, and the belts stop, the whistle will continue for about a second, they very vacuum-like, die out and raise in pitch over the next 2 seconds.
I thought it was my TB, so I took off my intake elbow and while the car was running I put my fingers around the edges of the blade, and tried closing off all the separate holes inside where air was being sucked in and none of this effected the whistle in any way (except making the car slightly die out).
I listened as best I could, but I could not locate exactly where its coming from... at times its sounds like in the front of the engine, and other times seems like its coming from the back of the engine. Its a newly rebuilt LS1 and I only have about 200 miles on it. Its been doing this ever since I got it running properly.

I just can't figure out what would cause the whistle only once at operating temperature and only when its at idle, or barely open throttle.

Please guys, any help is very much appreciated.

Any suggestions?

Thanks,
John

[SteveCZ28]

i had this happen on my z28 also...theres a little black vacuum hose behind the throttle body on the passenger side. it has a 90 degree bend in it..its really soft rubber. mine had a hole sucked right thru it. got a new hose then was perfect again. might wanna try that

[Cutlass]

Its probablly a vacuum leak of some sort. Maybe the intake gaskets, injector o-rings, PCV hoses, brake booster hose, other vacuum hoses. A good way to find it is to spray throttle body cleaner or carb cleaner around suspect areas. If the spray gets sucked in the noise will change a little and the idle speed should change. If you don't wanna use TB cleaner, I've also used a garden hose with no nozzle on it and dribbled (sometimes drenched) water in various areas.

[jbai322]

good ideas, I will try them both out and see if I find out anything. I really need to get this figured out before I go to an upcoming event.

Any other possible suggestions if those don't work?

John

[GatorSS]

Sounds like a little crack or pin hole in the PCV hose.

[jbai322]

yea, I'll try the carb cleaner idea. Probably my best bet at locating it right now.

[jbai322]

Alright guys, I figured out how to eliminate the whistle noise, but I was wondering if what I'm doing to stop the whistle is bad for the engine.
I figured out that if I squeeze shut the vacuum hose that runs between the intake (just behind the throttle body on the passenger side) and the passenger side valve cover, the whistle goes away and it continues to run fine. Is this bad for the engine to block off those ports? What does that hose usually do? other than make my car whistle!
So, the question is, will it do any harm if I eliminate the hose?

I tried the carb cleaner with no luck, I sprayed everywhere with no rpm rise... except when I did it on my air filter...

Input very much appreciated,
Thanks,
John

[SteveCZ28]

well, then more than likely there is a hole in this hose...i think its for the pcv or something like that, this is the hose i was talking about when i posted earlier, as i had the same exact thing happen to mine...its a very simple fix, its less than 3 inches so most parts stores will just give u the hose for free

[jbai322]

alright, I'll give it a shot.

Would blocking off the hose do any damage?

John

[SteveCZ28]

im not sure about damage on blocking it...i wouldnt recommend it, as you see a difference in plugging it, and leaving it open.

[mark21742]

alright, I'll give it a shot.

Would blocking off the hose do any damage?

John

the ls motors generate a lot of crankcase pressure, specially at higher rpms, you have a few choices.... you have the hose going from the valve cover to the back/top of the tb (this is the hose you are having the problem with). the second vent comes out of the front/top of the bellypan cover and goes to the front/side of the intake right behind the tb.
if you block them of too much pressure will buildup in the crankcase.
1.) you can just replace the hose.
2.) plug the ports (1 in the intake, 1 in the tb) run a hose from the vent ports in the valve cover and front of the belly pan into a (T) and on the opened end of the (T) put a small breather... Sarge will probably counsel me for it but this is what I did...you will occassionally get an oil smell from time to time.
3.) the option you should go with(like I said above I did not do this yet) is a catch can so you suck the pressure and burnt oil vapor out of the crankcase.


if you look around in here a few weeks ago Sarge had a very good writeup for the pcv delete/ catch can install

I hope I helped!

[jbai322]

cool, I will give it a shot.

Thanks guys for you help.

John

[mark21742]

cool, I will give it a shot.

Thanks guys for you help.

John

hey not a problem, know just about every question I've had someone on here was able to answer, so if you have any more just ask.

[jbai322]

Good news, I fixed the problem! I think what I did is ok, let me know if it isn't.
I disconnected the hose from the intake and plugged that hole (on the passenger side), and I put a breather/catch can on the valve cover side of the hose, runs the same and no whistle!

Thanks for the help guys, and if there is a problem with what I did, please let me know because I really don't want to harm the engine.

Thanks again,
John

[Cutlass]

so you plugged the intake hole and put a breathe on the valve cover. If so, than yes thats ok!!