I had my wife turn off the motor as I stood over the engine amd I could hear what sounded like air either being sucked or escaping. The noise could have been coming from around UIM, pressure tank or vacuum tank....from that area it seemed.

YOU CANNOT HEAR IT FROM INSIDE THE CAR. YOU HAVE TO LISTEN TO IT WITH THE HOOD UP LEANING OVER THE ENGINE.

This is the first time I've ever heard the engine turned off while standing there with the hood up so maybe it is normal to do this.

After recreating the sound, I pulled a hose off the pressure tank and it still had pressure.

So is this normal or not? Anyone else getting this?

 

So do I have to bribe you guys with **** to get you and some goon to listen closely when you turn the car off?

BTW my car is stock.

 

maybe the hot water, which produces pressure ?? the pressure caused by steam is coming out of the radiator, can it be?

 

Matt, I will check mine later on today and let you know.

 

Just got back. When the motor is shut down I hear what sounds like a sigh coming from somewhere down in the engine (same as you describe) that lasts for maybe 1 - 1.5 seconds. I also tried to take a hose off of the pressure tank (not super-duper hard, but hard enough that it should have come off) and it would not budge, almost positive it stayed under pressure.

I don't know what you've done so far but since you've got an 8-5-5 boost pattern and you're still stock, you've got a real good chance of having a clogged precat.

 

Did anyone ever stop to think maybe its the noise your car makes when it stops pulling vacuum and starts equalizing?

 

Nope...I'm not so bright under the hood of a car.

So is that it or a guess?

 

I was told by one owner today it is nothing to worry about, but I'd like to KNOW if that is so and what the heck it is.

bond007 suggested the same thing and has been kind enough to help thru some troubleshooting. Tomorrow should be revealing. Not sure if I can execute all of his suggestions, but he has been patient.

 

Thats it. Listen to almost any car, they all do it. My car does it, my friends 3000GT does it, my other friends miata does it... Any car with a fairly-open intake system will make the noise. The action of the the manifold equalizing ALWAYS happens...Its just that with a restrictive intake system, you wont be able to hear it as well.