Very loud hissing sound...

[Shaun 97VIII]

Just last night I noticed a very loud hissing sound comming from under the hood. It sounds like a really bad vacuum leak, or maybe a bad idler pulley bearing. so I pop the hood and the sound was even louder, louder than the engine itself!
it seems louder on the passenger side of the engine than the drivers side. so i again thought idler pulley.... no. i go to shut the car off and it resembled the sound of air being let out of an air-compressor for about 4 - 5 seconds after shutting the engine off.
any ideas?
thanks!

 

[67Continental]

could be a hole in your airbag, that side?

 

[Shaun 97VIII]

hmmm, yeah either that or a line got knocked loose somewhere around the compressor??? i never even thought of the air-ride to be at fault
i dunno

 

[Grifter]

if the vacuum leak was that bad that you could hear it that easily, you sure would know it by the motor running horridly, or not at all. When i forgot to put the vacuum hose for the brake booster back on my intake, it started the car and it wouldnt even stay running, when it did run it stumbled badly.

 

[rmac694203]

Just flip the air ride switch in your trunk and that will disable the compressor. If you still hear the noise then it's not your compressor anyway.

 

[Frat-man-du]

Just flip the air ride switch in your trunk and that will disable the compressor. If you still hear the noise then it's not your compressor anyway.

:iconcur:

 

[MrWilson]

you got a cobra hidin under the hood! haha

 

[Shaun 97VIII]

you got a cobra hidin under the hood! haha

lol, yeah no kidding.

i have ruled out a vacuum leak because I am still getting 26-29mpg highway, and idle is good and I drive 44 miles r/t everyday.
i also ruled out hole in the airbag because the car still airs up normally and stays level overnight. i will try the air-ride switch tomorrow.

 

[NYC LS8]

If it was a bad o-ring where the dryer meets the compressor, the car would drop all four corners. I had that happen on my '95 and boy was it a loud hissing.

Also, remove the serpentine belt and see if it goes away.

 

[JRMARK8]

did you check your air intake box maybe something flew in there thats making a sound or your cats could be cloged or the exhaust has a crimp somewhere.

but I'm not sure if that could ever happen.

 

[MarkVIII93]

I hear the same exact noise on my car....

 

[Shaun 97VIII]

definatly not the air suspension, it would drop like NYC LSC said. and i hit the switch and it didnt go away.
i am thinking clogged PCV valve perhaps? and my car is about 500miles overdue on the oilchange