I recently purchased a 2008 Cobalt. I have noticed when I turn the car off it gives of a blowing sound. I have a typhoon kit installed also.

In addition to that I noticed the as I drove between a couple of cars at low speed and accelerated it sounded like I may have a small exhaust leak. I went to check the exhaust manifold bolts and when I went to tight them up they seemed to turn rather easy so I stopped because I didn't want to over torque the bolts.

Anybody familiar with the blowing sound? It is only noticeable with the windows down. Is this due to the Typhoon? What are the torque specs on the manifold bolts? Should they be able to be tightened?

 

I'd say every car with an intake will make a "whoosh" sound when you turn off the car. When your throttle body closes, air flow is cut off making the sound you hear.

 

Best way to check for an exhaust lesk is when the engine is cold. Start it and put your hand where u think it's leaking. You'll be able to feel the leak.

 

When the car is idling, there is vacuum about 10-15Hg. When you shut the car off, the throttle body opens slightly to "bleed" off the vacuum. That is the woosh sound that you are hearing.

And on the exhaust leak; just run your hand around the exhaust like deebalt said. But make sure to check when its warmed up too; just be careful...smelling your own burnt/sizzling skin isn't as much fun as it sounds...

 

If u still can't find it then find someone with a smoke machine. My favorite tool for hard to find leaks. Lol. Good luck

 

You could try Seafoam, I bet you'd see that smoke.