I've got a 2000 Outback wagon thats due for inspection soon and have been plagued by a unidentified noise for a few months. It came out of no where and I cannot pinpoint it. I have ridden in the back seat and listened as well as the hatch. I can tell its in the rear. it sounds like a loose bolt where the washer is rattling around at a high frequency... I have check for loose bolts. I described it below in the recommended form, Any additional question post them up, I want to find this gremlin.
A. When does the sound happen?
When engine is running
_ When transmission is in some particular gear
_ When turning
_ When braking
_ Over bumps
_ In cold conditions
_ At speed - wind noise
Specifically under load between 3000-4500 RPM. Throttle above 50%
B. Where does the sound come from?
C. Does the sound vary with some condition?
Engine/transmission rpm dependent
_ Air speed/direction dependent
_ Varies according to some other condition
If I accelerate slow I don't hear it, but over 50% throttle it starts at 3000rpm and fades by 4500rpm. Intensity/ Speed increases based on throttle application such as 50% to 75% or WOT.
D. Is there a vibration associated with the noise?
_ Feel it through the floorpan or seat
_ Feel it through the steering wheel
_ Feel it through a pedal
It sounds like a vibration but no change in feel when it occurs.
E. Does it affect drive-ability? how? (Essay question, 2500 words or less)
No, Just randomly started a few months ago. I listened in on the fuel pump with the cover off, no additional noise. Have replaced an axle all rotors and pads all around, went on quiet and still are. All fluids have been replaced and maintained. Exhaust was inspected and gaskets replaced. I am beginning to think it is the evap system but I looked it over and felt the lines, everything seems intact and connected.