My GS430 is about two months old. I've just started noticing a pump noise coming from the back, after the car starts. Here's the scenario: A/C is off, audio is off. Turn on car. Wait 15 seconds or so, and a hissing pump noise starts coming from the back. From the driver's seat, it sounds like it's coming from the sub woofer.

It loudness varies, but it seems to go on for a long time. It sounds like the fuel pump or the tank being pressurized. However, I sat down in my friend's 06 GS300 RWD, and there is no such noise.

This is starting to bug me...anybody else having similar issues?

 

I have noticed that noise also. I think in mine it is louder when the air conditioned seats are on. I notice when they are on high i hear it when they are off there is no such noise

 

I also hear the same sound,i'm not sure what it is.In tank fuel pump?

 

I'm going to mention it to the service writer when I take the car in for my first service. If it's a normal sound, I'm fine with it, but I'd like to know what it is.

I'll try turning off the seat air and see if that makes a difference, I hadn't thought of that.