After I turn the engine off and step out of the L, I hear a "psshhhhhh" like noise as if air is being bled from somewhere in the engine compartment (supercharger?). It only lasts for like a second but I am curious to know exactly what it is.

 

Are you leaving the A/C on???

 

Thats a negative.

 

I'm guessin it's your a/c...

 

Isn't there something to do with the EGR that changes position when on/off?

My truck makes a "noise" when I shut it off. It's not a Lightning though.

 

It's probably your A/C. Did you turn it off just before shut off? If so, it's probably the A/C compressor bleeding off (or something like that) Mine does it if I park it, turn off the A/C, then turn off the truck. If I turn off my air when I pull into my apartment complex, by the time I shut the truck off, the sound isn't there. Hope this helps! Good luck.

 

I know what you're talking about, I hear it too, and I almost never run AC. I can't answer your question though, sorry.

-Ollie

 

I hardly ever run the AC. I called SVT and they said it was most likely a discharge of back pressure from somewhere. Hows that for a technical answer? Anyone else with any ideas?

 

how long do you hear this sound for?? on my truck i hear it for a little while probably close to a min i figured it was just like a pressure release from the air intake but im a retard so i like to make things up so i feel better



Later....

 

If you let off abruptly its most likely belt slippage.

 

My truck does the same exact thing. I always thought that it thought that I was always trippin' from not driving it hard enough and would always go "pppphhhhhssssss" when I killed it. I don't it isn't anything serious.
I think it is the air filter discharging the extra air back out of the filter after the blower stops.

 

Watch your boost gauge the next time you shut down. When idling, just before you turn the key to off, you boost gauge will be pegged on the vacuum side. When you shut off, the "pppphhhhhssssss" sound will begin, and the gauge will slowly sweep to zero. Notice how the sound changes as the gauge approaches zero – and when it gets there - the event is over. So do you still think it’s the A/C???

 

You hear it more if you ahve an open air filter, it is the vacuum from the boost controller releasing.

Daniel

 

Thanks for all the replies. I am going to write this off as NO (Normal Operation). Peace!