Hissing noise: Saturn Vue

Hi! This morning when I pulled into the garage after taking my daughter to school and shut the car off, I noticed a very loud hissing noise coming from the back end of my car, underneath somewhere. When I came back out an hour later to leave for work, it was still hissing. I drove to work and all was fine, but when I went out to the lot after work my car was completely dead. I tried jumping it, but it wouldn’t even take a charge. I had to find a ride home and will get it towed tomorrow. I’m sure the hissing noise is the cause, but I’m dying to know what anyone’s thoughts are on what’s going on. My car has never given me any problems–it’s run perfectly for almost 150,000 miles (5 speed manual transmission). Maybe this is the end?

What year, and which engine choice?

Does your car have a leveling system in the suspension?
If so, then that would explain the hissing noise that was running on and on.

When you say the car was completely dead, I am assuming that you mean that there wasn’t enough electricity to turn on the radio?


2002, 5-speed manual transmission

I’m not sure if it has a leveling suspension.

Yes, completely dead–not even enough juice to turn over. This morning when it was connected to a battery jumper, the hissing started again but still wouldn’t start. So whatever that hissing noise is, it’s something that needs power to do it and it’s obviously draining the battery.

The problem with thinking that it is an auto air leveling system is that a hiss would only be hearing a leak. It doesn’t take any power for the air to leak out. That would come from the compressor kicking on to replace the lost air. But the compressor doesn’t sound at all like a hiss - it sounds more like a grumble.

The problem with not thinking it is a auto leveling system problem is that I can’t think of a single thing back there, other than that, that would draw power and involve a hiss.

Is there more to the sound that you might be able to describe? You said from underneath somewhere, so I’m assuming that means outside of the car. Is it outside of the car?

I’d Try Pulling The Fuel Pump Fuse / Relay And See If The Noise Stops.


Well, I just heard from the garage. They said the hissing noise is the fuel pump but that everything is working. They said that the alternator “must” be bad because the battery is completely drained. When I said, “well couldn’t whatever the hissing noise was have drained the battery?” there was no response. They said they’d keep checking.

Can’t an alternator be tested? I’ve had cars with bad alternators before and there are symptoms before the car finally dies and won’t start again. I’ve had NO symptoms. My car has started perfectly in the below zero weather we’ve had for the last two weeks. This hissing noise started and remained on when the car was shut off and then I couldn’t start it again. They’re trying to tell me they’re not related. I guess I’m having a hard time accepting that!

Based on the fact that you said it started hissing again when you put a jumper box on it I’m inclined to say that their diagnosis is bogus. And yes, alternators can be tested. I’d ask them what they did to test it and get them to keep looking.

If you want to be ambitious, get a full charge on the battery (w/ a charger) - go to the fuse box and start pulling each fuse one by one until you find one that stops the hissing noise. Then you’ll have a very small number of options to consider.