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#1051541 - 06/16/17 10:51 PM Noise under hood after engine shut off  
Joined: May 2007
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1988SS Offline
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1988SS  Offline
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Joined: May 2007
Posts: 48
Georgetown, TX
I have a stock 1988SS. Sometimes....when I turn the car off, I hear a sound coming from the carb area. Lasts sometimes up to several minutes. It is a low pitch hum...sort of a wah.wah.wah. Hard to describe with words. Any idea what I'm hearing? Thanks for any help. Darron

#1051542 - 06/17/17 12:39 AM Re: Noise under hood after engine shut off [Re: 1988SS]  
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spacemanspif Offline
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spacemanspif  Offline
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Swedesboro, NJ
Are you hearing it while you are in the cabin or with the hood up listening for the noise? I'm wondering if it might me the blower fan spinning down if it's a noise you hear while in the driver's seat.


-Mike

F-body bucket seats, camaro console, carb'd 5.3/4L80E swap

Fastest time to date: 13.671 @ 103.79
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#1051543 - 06/17/17 12:49 AM Re: Noise under hood after engine shut off [Re: 1988SS]  
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1988SS Offline
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1988SS  Offline
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Georgetown, TX
When I turn the car off....I can faintly hear it in the cabin.....I can then open the hood and can hear it coming from around the air cleaner / carb area. Haven't removed the air cleaner while it is happening to try to pinpoint it better yet. It usually stops after a minute or two. Doesn't always do it.

Last edited by 1988SS; 06/17/17 12:50 AM.
#1051545 - 06/17/17 06:00 AM Re: Noise under hood after engine shut off [Re: 1988SS]  
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
There is a reservoir that retains vacuum, some call it the vacuum ball, it's located under the hood usually in the left front corner. After the engine shuts off it should retain vacuum for a while because there is a check valve in the supply hose which is connected to engine vacuum. If the check valve is bleeding off the vac from the ball back to the carb/intake manifold you may hear that after shutting off the engine.

Location of the check valve is usually in the area of the cruise/throttle cable bracket, but it varies depending on year.
Bob

#1051574 - 06/19/17 01:20 AM Re: Noise under hood after engine shut off [Re: mmc427ss]  
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JMonte7892 Offline
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JMonte7892  Offline
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Baltimore, MD
Originally Posted by mmc427ss
There is a reservoir that retains vacuum, some call it the vacuum ball, it's located under the hood usually in the left front corner. After the engine shuts off it should retain vacuum for a while because there is a check valve in the supply hose which is connected to engine vacuum. If the check valve is bleeding off the vac from the ball back to the carb/intake manifold you may hear that after shutting off the engine.

Location of the check valve is usually in the area of the cruise/throttle cable bracket, but it varies depending on year.
Bob

I second this


1983 Monte Carlo Sport Coupe [sold]
1984 Monte Carlo Super Sport [deathmatch with a Santa Fe]
1985 Monte Carlo Sport Coupe [frame-off in progress]
#1051632 - 06/20/17 11:32 PM Re: Noise under hood after engine shut off [Re: 1988SS]  
Joined: May 2007
Posts: 48
1988SS Offline
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1988SS  Offline
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Joined: May 2007
Posts: 48
Georgetown, TX
Thanks for the replies. I'm not sure which is the check valve, but I will try to pinpoint it when I hear it again. Is this something that should be replaced?

#1051642 - 06/21/17 03:08 AM Re: Noise under hood after engine shut off [Re: 1988SS]  
Joined: Jan 2000
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
It will look something like this.
https://www.summitracing.com/parts/smp-dcv1/overview/
Bob


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