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Loud intake whistling problem


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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

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no, I don't think it can be a head gasket because when I give it throttle the whistle goes away, then back at idle it will whistle again. when it dies out below idle, it goes away, and when I turn the car off, it will continue (after the belts have already stopped) to whistle as it rises in pitch for just a couple seconds.

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It's not coming from your brake booster is it? That might hold a vaccum after turning the car off. Disconnect it and see if it goes away(plug the intake port that it's going to though so you dont have a leak).

 

Guy

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Do you have a super charger lol. No J/K.. If it's that loud I doubt it's the vacuum leak. It's the friggin belt. Remove the belt and start the engine and check it out. I had a problem with the tensioner pulley's bearing goes bad and making the whistling like sound so damn loud one time. Good luck.

V.

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Do you have a super charger lol. No J/K..

haha, I wish, then I would have an excuse to tell people what the noise is. "My super charger is so big you can hear it whistling from 2 blocks away!"

Nop, naturally aspirated.

 

It's not coming from your brake booster is it? That might hold a vaccum after turning the car off.

I thought that could be the possible problem and I tried blocking it off already, but it didn't effect the whistle.

 

 

I will try to get some sound for video clips up and post them.

 

 

Thanks for the help,

John

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Fuel Pressure regulator? A vacuum leak in the vacuum side or maybe just the fuel flowing through it under idle conditions causing the whistle? Maybe try disconnecting the vacuum line to the Fuel Pressure Regulator while its whistling.

 

Does your car have the vacuum operated climate control, i.e. factory A/C, if so, is it connected?

 

Keep us posted.

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Also, maybe pinch/restrict the fuel return line before the fuel pressure regulator and note any change in pitch. Only do that if you know for sure the rest of the fuel system can handle the spike in pressure. I don’t recommend restricting the fuel line after the regulator as that adds more stress to the diaphragm inside the FPR, depending on how much pressure you pump is capable of producing, the FPR may handle it just fine. In short, just be sure everything is up to snuff if you try this as the pressures will be greater.

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no a/c, no power steering, no smog. The whistle continues even after the car is turned off just for a couple seconds. I don't think its the fuel reg., although thats a good guess. I've had more than one problem with my fuel reg already.

Its so loud, that its hard to pinpoint the location. I will try looking it over again.

 

John

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Also, maybe pinch/restrict the fuel return line before the fuel pressure regulator and note any change in pitch. Only do that if you know for sure the rest of the fuel system can handle the spike in pressure. I don’t recommend restricting the fuel line after the regulator as that adds more stress to the diaphragm inside the FPR, depending on how much pressure you pump is capable of producing, the FPR may handle it just fine. In short, just be sure everything is up to snuff if you try this as the pressures will be greater.

 

thats not a bad idea, I will mess around with that a little. I'm willing to try anything at this point. Someone suggested using a stethoscope, but I'm not sure if that loud help cause the noise seems to be reverberating throughout the whole engine bay.

 

Thanks,

John

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The fuel pressure regulator and the fuel pump are designed to hold fuel pressure after the engine is shut off, but some do leak, even brand new. If the fuel pressure is rapidly bleeding off over a couple seconds time span after the engine is shut off?…..

 

Also might try just disconnecting power to the fuel pump while it is whistling and note any pitch change as the fuel pressure drops and the engine starts to stumble and die.

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Hey! You're in San Diego huh? Where abouts are you located? Maybe I could cruise by and have a look. :-)

 

yea, actually I'm down here in san diego, but the car is up in redlands area. I go to school down here, and work on the car up there. I go up there every week or so and will soon be out of school so I'll be up there more. Hope to put some mufflers on the car and bring it down here for some qualcom autox's. I'll let you know when I bring it down here. Thanks for the offer, but hopefully I can fix it before I bring it down here.

 

John

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  • 2 weeks later...

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?

 

Input very much appreciated,

Thanks,

John

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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?

 

Input very much appreciated,

Thanks,

John

 

Its to suck out blowby and recycle it back through the engine if i'm not mistaken.

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