Here's a gem for you guys...

When I shut my truck off it makes a faint whining noise almost like a vacuum leak. I can get it to do it about 90% of the time and sometimes it's louder than others. The dealer couldn't seem to "duplicate" the problem and replaced the IAC thinking that was causing it. Well, lo and behold, I pick it up this evening and pull it in the garage, shut it off and there's my faint whining sound from under the hood again. Started it and shut it off four more times and it did it every time. It only occurs at shutdown that I can hear and it's a faint whining (almost like letting the air out of a balloon with the end pinched but lower pitched). Mods are in my sig and the truck has 2900 miles on it. Any ideas so I can point the tech in the right direction when it goes back in for a new fog light?

Which is another gem story as they weren't originally going to warranty it...SVT and Ford Customer Service quickly straightened them out on that one. Two days at the dealer and they didn't manage to fix the light as they had to special order one and my noise it still there...glad I'm under warranty and didn't have to pay their $131 bill for nothing.

 

That wining you are referring to is your A/C freon going back to were it is supposto be in that silver can on the passenger side fire wall.

 

SIA
Mine does the same thing too, not all the time but fairly often.

Jim told me what it was, but I guess I am getting old as I forgett what he told me.

It isn't anything to worry about.

 

I didn't figure it was a big deal but it is one of those things that draws stares when you shut the truck off...kind of like a sneaky little fart that you think no one will hear...and I thought a chip got rid of all my farting noises!

 

Mine does it too, always has.. It did get more pronounced after I installed my JL Ram air Kit. I also have a '92 Bronco that has done that same thing since day one, bought it brand new.....It's nothing to worry about....just my opinion though.....JR

 

Just tell people its the turbine spooling down...

 

Dan,

Watch your boost gauge the next time you shut down. Does it slowly go back to zero after the engine stops? Does the audible volume of the hiss seem to coincide with the gauge readings, the hiss ending when the gauge finally reads zero? After the engine is completely stopped (RPM=ZERO), open the throttle wide - did the noise instantly extinguish?

Let us know what you find…… Joel

 

Joel,

What's going on you ol' dog? Haven't heard from you in a while...you ready to head to the track again when it cools off some more?

I actually did what you had asked and the noise happens at shut-off and as the boost gauge drops back to zero it does stop. I've got the Lunar boost gauge and at idle I'm pulling about 15-17 in. of vacuum. The noise goes away when the gauge hits about 5 in. of vacuum. If I start the truck and shut it off and immediately floor the gas pedal the noise goes away instantly. What's the deal o' King of all things that flow?

Thanks in advance,

Dan

 

Although you and I talked about this on the phone, I'll post this for the masses......

Your first intuition was exactly that. These throttle bodies seal fairly well. In the old days of carbs, they were always slightly angled open. Now we have the IAC solenoid to create that small leak during idling, no need to angle them open. Plus there is that lovely oil mist assuring a good seal.

My theory why it is more pronounced on our lightnings goes like this:
1. The open filter no longer muffles this noise. I've switch the airbox and open filter out and notice that you can hardly hear it with the OEM box.

2. The addition of the EATON and associated hardware significantly increases the intake volume, prolonging the vacuum leak.

Dan, It was nice catching up. I’ll see you at the track once those 80 degree highs greet us again.

Joel......

 

And I'll add to the posting for the masses...

I first noticed the noise after doing the "oil separator" mod and removing my breather cap...figured I didn't need it any more with the aforementioned mod. Since hearing the noise I have left the oil fill cap on and removed the "oil separator" mod. After speaking to Joel I did a little experimenting with the truck. No "oil separator" and removed the oil fill cap and no noise. Added the breather cap on and no noise. Put the "oil separator" back on in combo with the breather cap and my noise is still gone. Figure the breather cap just allows the truck to "bleed off" vacuum faster at shut-down and hence no noise.

Interesting little thing though and wondered why I never heard it when the truck was stock...ahh, the wonders of Ford.