For the first time, last night, I drove with the back seats folded down beacuse i had to rest something on the seats and didn't want to put them on the seats themselves. so I rested them on the backs of the back seats after folding them down.

After a few minutes of driving I started noticing a hissing sound... Almost like stereo feed back.

Took the stereo off and still made the sound...

The best way I can describe it is kinda like the sound a tank of compressed air makes when filling up a balloon.

Dont hear it with the back seats closed... so I assume its from the trunk... started thinking it may have been from the exhaust? If so, is that normal?

I've got Corsa Sport Axle Backs on the car.

Thanks!

 

Must be an exhaust leak. With the engine running, take a balled up large old rag and push it into the muffler tips (do one at a time). Don't get burnt it will be hot. You should be able to hear the leak better if its an exhaust leak.

 

Mine does the same thing when I have the back seat down. I play hockey twice a week and I have to put the one seat down to fit my sticks in.

It makes a hissing sound, but only if I get over about 40mph. I don't think it's a leak, it might just be air coming through the trunk while driving at a certain speed. I've had my car since May and it's always made this sound.

Of course you cannot hear the sound when you put the back seat back up.

 

Weird indeed... car seems pretty solidly built to have THAT much sound come through from wind... I mean I can see road noise but it definitely doesn't sound like normal road noise.

 

The sound is probably coming through the cabin air baffle.

 

It's what lets air out of the car when you slam the doors or you run the heat/ac/ If you didn't have one your ears would pop when you slam the door and the heat/ac doesn't work as efficiently because it works against the cabin pressure.

 

Indeed. Probably that combined with road noise and air whirring around in the rear wheel wells that is normally more muffled when you have the seats up.

 

Ah ha... makes complete sense now... Most importantly... nothing's wrong with the car... its perfectly normal... thanks!

 

Mine does the exact thing you describe. Glad to know it appears to be normal.

 

Could it be due to cabin pressure being different than the outside.

 

Well that is likely part of it. Air flowing through the baffle in the trunk. But if you ever get under the car and take a look at the wheel wells and muffler areas you can see that there is a lot of space in there for air to pack and swirl around, which is definitey adding to the noise when you have the seats down.

 

There is also an Evap control cannister and all the related vacuum lines, along with the fuel pump making noise..