noise from rear in idle
 

i've been searching posts for the last hour but haven't come across anything that i was sure was the same as what i have.

basically, when parked and in idle, if i stand behind my car, i can hear a mechanical whirring/rattling sound. it's not *too* loud, but it doesn't sound like a good or "healthy" noise. i can't hear it when in the car, and i don't hear anything when driving. is this normal? i've already busted up a differential...hopefully this one's not about to go also. the sound doesn't go away no matter how long i've been driving.

i just hit 50k miles. just changed the diff. oil (mobil 1 75w90) a few weeks ago, and that was a brand new differential (about 4k miles from install to first change). i could hear the sound before, so the change didn't really affect the noise. i will be changing the transmission fluid tomorrow. as far as i know, that hasn't been changed before. any ideas? i'm guessing it's either the transmission or differential? thanks for any replies.

[QUOTE=benighted,Mar 18 2006, 09:00 PM]
basically, when parked and in idle, if i stand behind my car, i can hear a mechanical whirring/rattling sound.

i'm not exactly sure where the trans is located actually...i'll see if i can hear it from the side tomorrow. can definitely hear it from the back...sounded like it was coming from the area under the trunk but i'm not certain.

Maybe the fuel pump is taking a dump.

Whirring (like a little jet engine) would be the fuel pump.
Rattling could be something loose in the exhaust system. Stand back there and have someone slowly rev the engine a bit. This might give you a better clue.

it is definitely a whirring sound. it only has a "rattle-esque" sound because the whirring sounds so bad. it's like there are metal parts grinding on each other, with little to no lubrication.

assuming it is the fuel pump, would that be the only thing that needs replacing? wanted to get an estimate. haven't been out to the car yet...doin that right now...i'll try those things you guys suggested and post again in an hour or two.

If that's what it is, it may be a normal sound. Before spending this kind of money buying a new one, have it checked by someone who can recognise the sound or at least check the fuel pressure as per the service manual.

Here's an idea of prices, but changing it out is not an easy task. You are probably looking at a couple hours labour at a dealer.
You need #4:

http://www.slhondaparts.com/browse.asp?Mod...&ViewParts=true

ugh...well having driven the car for about 45 min. (highway + quite a bit of vtec)...i couldn't hear the noise anymore when i got out (idling and standing behind it). wasn't able to distinguish anything with the engine revved or disengaging the clutch. i guess the noise goes away after a bit of driving?

i dunno, i'm gonna change my transmission fluid now, and i'll post again when the sound is back. thanks for the replies so far.

Fuel pump whine is typically non-continuous and not always apparent. It can come and go, but it has no relationship with road speed or engine speed. When the engine is running, the fuel pump runs at a steady speed. As already stated, it can be perfectly normal.