Hissing Noise

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Nov 8, 2006 | 01:23 PM

basicbob

Thread Starter

Freshman User

Joined: Nov 2006

Posts: 41

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From: South Western New York

Hissing Noise

I am wondering what is making the hissing noise after I turn my truck's engine off. This may have been answered in another post but I can't do a search and don't have the time to look for it.

Thanks

Basicbob

2006 XLT 5.4l 4x4 Scab

Nov 8, 2006 | 01:42 PM

06supercrew

Senior User

Joined: Jan 2006

Posts: 471

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From: eastern nc

You don't have a Cobra engine in it do you? Just kidding, couldn't help myself.
Could it be the ac compressor? If you have it on defrost or the ac turned on it is running and if you turn the engine off it will make a kinda hissing sound for a few seconds.
I'm sure someone else will chime in with more ideas.

And welcome to the board.

Nov 8, 2006 | 01:49 PM

MIKESANDS

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Joined: Mar 2004

Posts: 397

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From: San Diego

Quote:

Originally Posted by basicbob

Mine does the same thing, sounds like someone is spitting on a hot plate..weird

Nov 8, 2006 | 02:03 PM

basicbob

Thread Starter

Freshman User

Joined: Nov 2006

Posts: 41

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From: South Western New York

That's exactly how it sounds, I thought it was the condensate water from the AC dripping on the hot exhaust pipe.

Nov 8, 2006 | 02:15 PM

abah

Senior User

Joined: Jan 2006

Posts: 109

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I hear the same exact sound when I turn my truck off. Im thinking thats its probably the belts, but i dont know.

Nov 8, 2006 | 02:51 PM

Rxman

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Joined: Feb 2006

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Me too. I notice it when I've used the heater; about 30 seconds of hissing. I too thought it was from the drip tube for the A/C, but then notice water dripping from a tube with a nut (sorry for terminology) just above the drip tube.
The water runs down onto the exhaust to give that "spitting on a hot exhaust" sound. Anybody else notice this drip from the tube with a nut? I was going to mention it to the service dept on next service.

Nov 8, 2006 | 03:11 PM

ford390gashog

Fleet Owner

Joined: Jan 2004

Posts: 26,007

Likes: 575

From: Brentwood,CA

its the vacuum canister under the battery box it returns to 0 psi after the engine is turned off.

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Nov 8, 2006 | 03:47 PM

Ferguson65

Logistics Pro

Joined: Mar 2005

Posts: 2,536

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From: southeast PA

Actually this has been discussed before. It's the pressures equalizing in the a/c system. A/c operates on a pressure differential principal, so whan you shut the truck off and you no longer have the compressor turning, there's nothing to push the refrigerant through the orifice tube/ expansion valve (never looked at which system it has), so the refigerant just bleeds through on it's own until pressures are equal, then it stops. Run the truck around with the a/c off, and it won't do it.