Odd sound from motor when shutting her down

[P5stillalive]

2003 95k.
When I shut her down I get a hiss/pressure reflief sound from the motor that I can simply not track down.
Any ideas? Sorry to be so vauge. Ill grab a video of her tonight.

Thanks!

 

[njaremka]

if you have an intake installed, its normal

 

[BRIAN_MP5T]

Normal. It is the Stored vacuum in the intake escaping out of the intake manifold.

 

[P5stillalive]

Normal. It is the Stored vacuum in the intake escaping out of the intake manifold.

Thanks guys.
Ive just been hearing this hissing and ive replaced every vacuum hose in the engine. We have had this car for 11 years, I guess she is getting old.