Import Racer

I'm not sure which section to post this in, so I give this section a try....
This started about 3 weeks ago. After driving my car, and sometimes right when I start it, I hear this sound coming from underneath my car at that back. This sound lasts for about 1-2 seconds, then goes away and comes back every 5-8 seconds (yes, I kept track of how long the intervals are). At first, I thought it was my hand brake, so I released my handbrake and kept my foot on the brake and I was still hearing it. So I parked on a straight road without me stepping on the brake and same thing. Now...the sound I'm getting is kinda hard for me to explain. It goes something like "wooo". Kinda like a hollow sound. I hope that helps. It's not a loud sound. Kinda faint. I heard it while I was in my car waiting for someone, with my stereo off. You can only hear it when there's not sound around you. I hope someone on here knows what I'm talking about and knows what the problem is. Thanks.

***** UPDATE *****

I think I may have found the problem, but not completely sure...

Now the noise seems to be more continuous as in it keeps going for a while before it stops. Then when it does stop, the sound comes back within 10 seconds. When that noise comes on, I opened up my cap for my gas tank and the sound went away. I then put the gas cap back on and the sound didn't come back, but after a few minutes, it came back. I then waited til that sound came back and opened up my gas tank cap again, and again, the sound went away. Would it be my lines or something? Maybe air in the lines?

Jugglez

Exhaust leak maybe? Jack up the rear, climb under there and look for holes or tears in your exhaust system.

PULOVR

Do you have a stereo? Subs? If you do, put your ear near them while someone else tries to duplicate what you did before.
See what happens.
Could be a bad ground, and the noise you're hearing might be comming from the rear speakers when they are off.

imported_94EG6HB

Maybe your mid pipe has a hole. Do you have a cat back or full exhaust?

Import Racer

I have a cat back...this doesn't happen all the time, but most of the time it does happen...I took it for a test drive yesterday, then parked it on my driveway with the engine running for about 10-15 minutes, and that sound didn't come back. So if there is a whole somewhere along the piping, wouldn't that sound always be there and be constant?

The G2 Racer

I had the same problem when I had a system, it was a bad ground.

Import Racer

Really???
But why would it make that kind of sound?

The G2 Racer

It's alternator noise. Very annoying. Great a filter for it.

punkindrublic

i'm not sure if its the same noise but when my deck is off, sometimes i can hear a weird noise from the rear. it is in fact my subs cause the amps how there wired (which obviously isn't right) dont shut off the conventional way. so they stay on yet they get no input from the deck. hence making weird noises.

another kinda cool thing is that if i disconnect the ground from the amps. leaving only the front speakers on. the fronts make a wistle type noise. it directly follows the engines rpm too. so it kinda makes me sound like i have a turbo. when infact its just shotty wiring by me.

The G2 Racer

That whining is alternator noise. I had it one my car. Get a filter and it will go away. Just may sure it's a good filter.

Import Racer

But the noise is coming from the rear, not under my hood.

Buddah

I agree. I think it's engine noise coming through your amp too...the easiest solution would be to get a Capacitor. They run anywhere from 200 to 1200 depending on make and model. I think in your application, the simplest Cap would do. That would fllter out the noise. It also gives your amp a constant power source without any spikes so you won't blow out your amp and/or speakers. And, you won't notice a drain in power electrically as every bass line hits...the power is drained from the Cap...it's like an over flow champer for power...but, you tap directly into it.

Import Racer

But I don't understand why this would happen now, after 7 years with my system installed.

Would you guys be willing to check it out if I come out on Wednesday?

Buddah

sure...that sounds good. Come out to a meet and I'll have a look for you.

The G2 Racer

It's feed back from the alternator. The speakers make the noise not the alternator.

Import Racer

***** UPDATE *****
I think I may have found the problem, but not completely sure...

Now the noise seems to be more continuous as in it keeps going for a while before it stops. Then when it does stop, the sound comes back within 10 seconds. When that noise comes on, I opened up my cap for my gas tank and the sound went away. I then put the gas cap back on and the sound didn't come back, but after a few minutes, it came back. I then waited til that sound came back and opened up my gas tank cap again, and again, the sound went away. Would it be my lines or something? Maybe air in the lines?

imported_94EG6HB

Maybe the gas cap door is loose and vibrating...

What happens when you leave the fuel door open...

Did you try to tighten the four gas cap bolts...

Maybe a bad exhaust hanger...

Does the exhaust have good clearance...

Import Racer

It's not a rattling noise. It's kinda like a humming noise.

imported_94EG6HB

Call me ..... (number removed for security reasons)

Bl4de

Import Racer,
Do you have a Hatchback, with a custom rear dash??
Maybe the dash is rattling/vibrating to the engine vibes...maybe...or not!