1998 SE: Today when I turned off my car I noticed a sound, like a whining or a humming sound coming from the tail of the car. It continued for a good 15 - 20 minutes before going away, but I couldn't figure what exactly it was. I know it is NOT the E-brake because it wasn't engaged. It sounds like it's coming from just behind the driver's side rear tire and wheelwell on the underside of the car. I'm not sure where my gas tank is exactly, but considering the gas cap is right there, it's logical. There is a bulge on the underside right behind the wheelwell, but I haven't found any info on what it is. Anyone know? Again, this noise occured with the keys in my pocket, which seems odd for a car with electronic fuel injection. Anyone heard such a noise? And/or fixed it???

MaxNismo1
'98 SE 5-Speed

 

i think its the fuel pump keep running? same thing going on with my car.

 

Sounds like the fuel pump is running for some reason... even though that should be impossible with the keys out of the ignition..... weird.

 

The evap canister and purge valve are exactly where you describe the noise... perhaps it was just the pressure from the gas tank being vented into the charcoal canister... not sure if this can happen with the ignition off but I wouldn't be surprised if it could (since there is quite a big of built up pressure in the tank after a drive - as evident when you pull up to a gas station and hear the hiss when you remove the gas tank cap to refill).

 

I was thinkin EVAP canister too...thats exactly where it is. See if you pull any codes off the ECU.

 

I get this hum to sometimes, it defintly sounds mechanical like a pump. I've assumed its normal as it's done it ever since I've had the car. I've been told its just the fuel pump running to keep the lines full so when you go to use the car its already to go. Makes sense anyway, lol

 

There is already fuel in the lines when you shut off the car. Drive the car and turn it off. Disconnect your fuel filter and look at all the fuel spill on the floor.

 

So my theory is flawed, it sounded good anyway

 

Relieving pressure inside the gas tank .... interesting ... and hard to argue. My car runs like a champ, so it doesn't seem like there's a significant problem with the fuel system. Strangely, it's never consistent. I would say I hear that noise roughly once every 15 - 20 times I shut off my car. I'm gonna trust that it's not a problem because I know plenty of Max owners who have experienced it also. Sounds like njmodi wins for the best explanation. Thanks for commenting everyone.

 

Just another thought on this... on my old car - the gas cap seal had broken - and after a long drive, there would be so much pressure built up in the tank, after I would park the car, I would hear all this hissing... and smell gas... I was like WTF? one day, I just sat and watched the car for a few minutes while it was doing this and I literally saw a stream of gas squirting out of the gas tank door.. (it only happened that bad when the tank was 3/4 or so)... so potentially you may also have a bad gas cap seal - you could try to replace the cap (< $5) and see if that changes anything.