Help With Eninge Hissing

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Feb 6, 2013 | 03:45 PM

Kyo

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Joined: Dec 2011

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Help With Eninge Hissing

Doing some more working on my 1978 F150 4x4 today.
replaced the transmission
-Filter
-Filter Gasket
-Pan Gasket
-Black Band Vacuum Modulator
-New Vacuum Hoses for the Modulator
-Flushed and cleaned the Metal Vacuum Tube for Vacuum Modulator
-Flushed the Trans and TC and Refilled with 11qrts new fluid ( did not drain cooler this time around ).
-Found and fixed all Vacuum Leaks That I could..

Still have a High Pitched Hissing Sound I can not Identify.. I can not find any more Vacuum Leaks, but one hiding some place would not surprises me.. Any ideas What that noise is?

Here is a Video.. Thanks..
https://www.youtube.com/watch?v=hqEi...ature=youtu.be

Feb 6, 2013 | 04:11 PM

JRB65

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Joined: Mar 2009

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Quote:

Originally Posted by Kyo

Is the truck Running Smooth? Is the Idle rough? I had a leak in my EGR plate under the Carb.. Not sure if your truck has one.
JRB65

Feb 6, 2013 | 05:56 PM

MikePacey

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Joined: Dec 2010

Posts: 600

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From: New Carlisle, Ohio

Spray carb cleaner around the base of your carb and all intake manifold surfaces. If the idle picks up you pin pointed your leak.

Feb 7, 2013 | 12:27 PM

wilcam47

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From: Idaho

Quote:

Originally Posted by MikePacey

Spray carb cleaner around the base of your carb and all intake manifold surfaces. If the idle picks up you pin pointed your leak.

This and it sounds like the typical carb noise/venturi...does the noise change with the air cleaner on?

Feb 7, 2013 | 02:35 PM

Kyo

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JRB65- Runs Smooth, Rough Idle when cold. Have yet to get the Choke to work ( have to use my foot to warm her up )

Mike- I will try the Carb cleaner idea after work to try and find any remaining vacuum leaks... Thanks

wilcam47- To be honest, It Could be the normal carb noise/venturi sounds.. It has been years since I last worked on a vehicle with a carb So I would not doubt me hearing things that are not there Or reading to much into things..

Yes and No, It becomes more Muffled with air cleaner on, But louder in cab when driving..

Feb 7, 2013 | 04:19 PM

wilcam47

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Joined: Feb 2013

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From: Idaho

could be a leak at the base plate of the carb too...or a uncapped vacuum tube at the base plate...check behind the carb sometimes I have forgotten to look behind there and find a port not capped..

Feb 7, 2013 | 06:29 PM

MikePacey

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Joined: Dec 2010

Posts: 600

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From: New Carlisle, Ohio

If you find all your ports are capped or hooked up I'd just go ahead and replace the EGR plate gasket and the carb gasket. Your looking at 7 bucks and 20 minutes worth of work. Even if that isn't it atleast you got fresh gaskets and won't have to worry about that.