ladyzed

iTrader: (4)

2004.5 350z, with a year old, brand new long block.

Just recently, is making a really high pitched hissing noise. Sounds like a dog whistle if I were a dog.

Its a high frequency, really annoying pitched sound thats on all the time, no matter what (AC on of off, rpm high or idle etc...)

Any ideas? Fuel pump?

Darryl

AutoDetour

Try opening up all of your vents inside the cabin.

tylerxfire

iTrader: (15)

might be fuel pump..u will have to determine where it is coming from

AutoDetour

True statement above. Turn the ignition on and see if the noise comes on. I have my interior stripped so that same noise is much more distinguishable from the back.

ladyzed

iTrader: (4)

UPDATE: No, it only appears audible when the engine is running. HOWEVER, I noticed it was gone until I refilled the gas tank to around half. It re-appeared. I remember when I first posted this thread, I just filled up as well.

So maybe fuel pump going?

I hope not. Can the fuel pump make this sound?

DavesZ#3

iTrader: (26)

Sounds like fuel pump for sure. When you fill up, the fuel pump is submerged in gas, that is either changing the load on the pump or allowing the pump noise to transmit through the tank easily.

It's kinda' odd as most pumps make more noise and the tank empties, not the other way around.