stookrider

Hi guys, my newly-puchased S2000 (2003 with 23k miles) has a mysterious noise under certain conditions that I haven't diagnosed, and I'm hoping someone can point me in the right direction. Details are below:

Typically I can't produce the sound unless I drive the car hard. Conditions where the noise appears:
(1) Hard driving (consistently above 5k rpms under load for 5-10 minutes or more).
(2) Hot weather makes the noise louder, appear sooner, and last longer (at night, it's hard to reproduce). The sound might also appear in really hot weather without hard driving.
(3) The sound goes away fairly quickly (probably less than a minute) after returning to normal driving conditions, unless it's very hot outside in which case it could last for a while.

Mechanical properties related to the noise:
(1) RPM-dependent whine/whirring (usually starts at around 5k rpms)
(2) Happens in any gear I have tried (1,2,3 - higher gears aren't feasible on the public roads) as well as neutral
(3) Happens both at speed and when stopped
(4) Turning the radio or A/C on or off doesn't change anything

The sound is hard to describe. It's more of a whirring sound than a whine. It almost sounds like a really high pitched vacuum cleaner or a lower pitched r/c car. Also:
(1) High frequency (close to a constant sound, not a discernible clicking/tapping)
(2) High pitch
(3) Pitch changes with RPM

So I have two questions:
(1) Can anyone help me point me in the right direction? From searching, some similar sounds are related to the drive belt system. Could the belt/bearings/pulleys/whatever else go bad after only 23k miles? FWIW, the car was garaged in Las Vegas for the first 9 years of its life.
(2) Is it possible I am damaging something when I cause the noise to appear? (AKA should I stop driving it hard for now?)

Thanks in advance for any help!

2000ths

one important factor is where on/in the car is the sound coming from?

stookrider

It's hard to be sure. The noise goes away quickly after hard driving so I can't really get out and listen to it. I'm almost positive it's not coming from within the car. If it's RPM-dependent, wouldn't it almost certainly be coming from the engine bay?

hillclimber

I'd sure check the alternator, and any other belt driven accessories, but you probably already have..

2000ths

sure could be from the engine bay... but RPM related noises can come from a lot of places. differential, axles, transmission, exhaust, etc. even just something on the car that's loose and rattling can be affected by the vibrations from various RPM.

stookrider

I haven't checked them yet. I'm not exactly sure how. I read that you are supposed to use a stethoscope/screwdriver on each component while the engine is running, but I'm not sure where to put them, seeing as the pulleys, etc are moving parts. Can someone tell me the proper way to do this?

Can I also spray lithium grease (or something else) onto each pulley/component one at a time and see if the sound goes away as a method of diagnosing the failed part?

The noise also happens while revving the engine when the car is not moving and/or in neutral, and it is a high frequency whining noise, so I don't think it is a rattling sound or from somewhere other than the engine bay.