thats a weird wistle. I've never heard that before. it sounds like some pressure is building up somewhere. so it doesnt do it at all with the a/c off eh. can you even tell where the whistle is comming from. I'm guessing the a/c is buildin up pressure somewhere and then when you shut it off it's escaping.
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HOMEMADE LIGHT BULB

 

thats what i was thinking, it sounds like its coming from the silver cylinder that is circled in red a couple posts up, or somthing down beneath that thing, the cylider has somthing to do with the air conditioning because two metal tubes coming out the top are icy cold and kurbycar32 said it was...lol.

 

all i can say is wow, thats freakin weird.
definitely not the intake. i think your right to suspect the A/C system, but if it is you wont be able to diagnose it yourself. i think because it whistles so long after the motor is off that its very unlikely that its a vacuum leak. after hearing the sound i would go back to horatio's suggestion about the vacuum actuated blend door, another thing that as a rookie i dont suggest you attempt to repair yourself. i think you should go buy the repair manual and look at the heating/AC section and find where that blend door is, stick your head near it, and make sure thats your problem. its very likely that you will need a mechanic to get this fixed, although i will commend you on providing excellent descriptions of your problem[sm=smiley20.gif]

 

Yea I don't intend to do any repair myself unless its really easy. I picked up the haynes manual last night and I found out that silver cylinder is an accumulator...yay im learning parts...lol, anyways would you be able to explain to me what the blend door looks like, and/or what it is, I am clueless as to what to look for, both when looking at the engine or the manual, I didn't see anything that stuck out that said blend door, but I havn't looked extremely hard, I was looking more at the pictures...lol

Imma start googling about it now

 

behind your dash is a big plastic vent system. at a point, air comes in thru one hole. cold air on one side and warm on the other. theres a vacuum actuated flap that "blends" the right amount of cold and warm air to make you comfortable based on where you place hot/cold dial on your dash. the theory is that when you shut down your motor and therefore stop producing engine vacuum, this flap is releasing the vacuum and making noise doing it. i think one way to test this would be to shut down the motor with the temperature dial in 3 spots: hot,cold and 50/50. im betting that at 50/50 you don't hear the noise because thats the natural position of the flap

 

i was reading further up and noticed the soapy water test thing ,with vacumn this test will not work simply because it is sucking it in not pushing air out so there fore it will not create bubbles
my father used to use WD-40 to test for vacumn leaks spraying it around or on the line that was thought ot be leaking and if it was then it either reved up or down depending on whether or not is was at the carb inlets sucking it into the carb and mixing with the air being fed into the intake

but none the less it does work

 

I just tried with temperature **** at cold, 50/50 and hot all with the same results, when you say "behind your dash" does that mean tearing apart my dash or like just behind the glove box, which i think the haynes manual showed how to do.

 

Sounds like its your a/c ,some cars will make the noise some dont.I think its from the pressure dropping in the system.If the noise bothers you shut the a/c off before turning the truck off.I'v heard that if you shut the a/c off and give it time to cool down it will last longer.

 

mine did that when istill had a clutch fan.......i took it off and since our trucks are equipped w/ an auxiliarry electric fan(comes on when engine is hot and or comes on when a/c and defrost is on)......took it out and walah....

 

no but it spraying it on a vacuum leak makes it gurgle and you can watch the bubbles get sucked in :-)