Sometimes when I shut my engine off, I hear a loud hissing noise coming from the engine. Is this the air intake, or is there air in my coolant system?

 

Do you have an aftermarket intake?
Usually you hear that hissing noise because the intake is producing that noise when shutting off the car.

If you have a stock airbox, i find it odd that you hear it. The resonators in the airbox should suppress that noise.

 

yeah, I had short ram intake, and I could hear hissing noise.

 

:harhar: intake perhaps

 

No, I don't have an aftermarket intake. I do have a K&N filter inside the air box though. I also took out some sort of white filter that didn't seem to be serving any purpose.

 

ok make sure you didnt take out the cabin dust/pollen filter first of all. second theres a little deal called the crankcase ventilation system. this purges all of the fumes out of the intake manifold to prevent any damage from occuring during the next start.