Hello all g35driver members, today I've heard an unusual sound i have never heard before from my G, it sounds like someone is behinh my car spraying a can of paint it comes and go(pshhhh.....stop....pshhhh.....stop...pshhh..... stop) from under the rearend of the car somewhere under the rear tires. The car is making the sound while i am idle. Any idea whats causing the noise? Fuel pump maybe?

 

Bro my car makes that exact same sound and I found out a few days ago just never had time to post on the forums. The sound is coming from underneath the car from the rear let me know if you found out what the problem is

 

Possibly exhaust rasp...?

 

Mine has been doing the same for a while too. It sounds almost like a tire is punctured but i checked all tires and they are good. Any help would be appreciated

 

All G35's do that. It sounds like it's coming from around the area of the passengers side rear wheel.

I think it might be a pressure relief for the gas tank due to the fuel return lines building up pressure in there.

 

Hey thanks for answering partyman i really apperciate it, correct me if im wrong but doesn't the sound from pressure building up in the fuel line sounds more like a whining noise?

 

It wouldn't be building up in the fuel lines, it would build up in the gas tank as a result of the fuel being returned to the tank. If the noise is what I think it is, it's just air being blown out of the tank whenever the tank pressure hits a certain level through a bypass/relief/vent valve, and possibly incorporated into a charcoal/vapor canister.

 

^^ what he said.

 

OHHH ok sorry im really **** about new sounds that the car make because i haven't heard this sound before.....or it wasn't loud enough for me to notice.

 

Not a problem... I'm the same way with all of my vehicles.

I had my G for a good year or 2 before I ever noticed this sound. As the owner and only driver of it, there really aren't that many situations where you put yourself in a quiet enough situation to be outside of the car and situate your body on the passengers side near the rear wheel to hear the noise while the engine is running. For me, I first noticed it one day after washing the car and drying my rims while the car was running. I will say that this is the only vehicle I've ever owned that I've actually been able to hear the venting noise though... not necessarily a bad thing.

If you want to verify that this is what the sound is coming from, do this:

1) Unlock both your drivers and passengers side doors (so that the fuel door will be unlocked)
2) Start your car up and leave it running
3) Get out and kneel down by the passengers side rear wheel and verify that the car is currently making the hissing sound
4) With the car still running, pop open the fuel door and unscrew the gas cap (it will be right above your shoulders as you're kneeling, so you don't even have to get up and move to do this)
5) Check if the hissing noise stops when you have the gas cap off of the fuel tank


If you have the gas cap unscrewed, the hissing noise will most likely stop because the pressure in the tank will not build up and will never actuate the pressure relief valve for the fuel tank.

Another thing to note... You might find that your car may not even make the noise at all on some occasions. Chances are that it will do it more noticeably when the tank is full of gas, since the pressure will build up quicker as a result of there being less empty space in the tank when it's full.... thus the rapid cycle of hissing, silence, and then the hissing again. When the tank is very low, there is more space in the gas tank for the air to fill up and also will take longer to compress to the point where it reaches the pressure necessary to trigger the relief valve (gasoline is much less compressible than air)... and when it does reach that pressure on a low/empty tank, the pressure won't continue to build as quickly as it would in a full tank, so it will vent in a quieter fashion. Ambient temperature and the severity of the heat of your vehicle's chassis at the time of inspection could also play a part in the likelihood of your car making the noise or not making the noise while you're out there testing it.

 

if you have your rear seats out and the contents of the trunk out it is more noticable. people tell me it sounds like they are on a airplane getting ready for take off.

 

Mine makes the same noise, kinda like a hiss kinda sound. When I went to investigate it o first thought it was the suspension. So I pushed down on my trunk and it made the exact same noise. Not sure if yours sounds like a hiss type sound but yea lol

 

idk..prolly fuel pump...leak in ur tire?

 

Ive never heard mine make this noise... I'll have to listen up for it next time

 

fuel pump cover was leaking on mine so i had rear seats out, you can hear the hissing then.