I recently bought a used 350z for a pretty cheap price. Of course it came with many minor crap I have to fix. Recently when I was taking it for a drive with the speaker off, I noticed that my car is making a weird hissing noise. There has been a previous thread that someone had the same weird hissing noise BUT they said it was coming from the engine compartment. I had a friend get in the car with me while I drove very slowly to try and identify where the sound was coming from, and we both came to the conclusion that it was coming from somewhere in the back, towards the middle (not far back). And no this is not the fuel pump (I looked up what the common fuel pump problems and symptoms and sounds). It's not a constant hiss, it's like hisss ---- hisss --- hissssssssssssss --- hissss - hissss. But the hissing noise is there throughout the whole ride. Sometimes it disappears but it's there about 90% of the time. I mean if I turn my speakers up I won't be able to notice it, but I was wondering if anyone else was experiencing this and have a solution?

 

Actually, it might be the fuel pump haha. My bad, but it's kind of loud. You can hear it very well. Are there any other reasons besides this? And if it is this can it be cured with sound deadening? I know I'm not looking at a Porsche or Audi or any of the luxurious sports car, but sometimes I like to drive home from work in peace and quiet. If I have to deal with it, so be it, love the Z anyways.

 

Did you check for exhaust leaks? They generally sound like a hiss and there is a connection to the y-pipe in the middle of the car.

 

Sounds just like mine - recently bought relatively cheaply. And I seem to have a similar hiss. Doesn't sound like a fuel pump, more like air escaping from something. If I park and let it idle while I'm outside I don't hear it. I think it might be the brake pads - I know mine need changing as I can hear wear indicator squealing as I drive. Pads on order and I hope I get them this weekend. I also need a rear wheel bearing so might be that. Also on order, should have this weekend.

 

Tell me if that fixes it. I'd appreciate that. I am about to sound deadener the fuel pump area which should be located where the stock bose subwoofer is at. I'll tell you how that goes once I finish dynamatting the trunk area.

 

Fuel pump is on the glove box side.

 

I have inserted the sound that it's making. It's the hissing noise throughout the whole clip. Ignore the clicks, I'm not so sure what caused that but that wasn't the primary issue. The main issue was the hiss u can hear clearly. Sometimes it stops for a second then comes back. Please help! The sound is attached in Voice 001. Thank you very much!

 

Fuel pump

 

Would you say that is normal? Or quite louder than usual. It's very clear in the car when cruising at night with the radio off.

 

It's the evap purging. Rear passenger side. Most Zs with a proper evap have a loud, inconsistent hiss from the rear. It's normal.