I have a '90 SE with manual transmission and 230K miles. Recently it has started making a high pitched sort of whining/whispering noise. I'm not sure how to describe the noise, but if you could put a bunch of squeaky things in a blender and run the blender at low speed, that might be close.

The noise seems to correlate mostly with speed. It isn't there at low speeds, then starts in and gets louder as speed increases. When I maintain a steady speed, the noise remains fairly constant.

Usually, disengaging the clutch, and putting it in neutral, don't have any effect on the noise. But sometimes the noise stops when I do that, before slowing down.

Any thoughts?

Pretty tough to say but it sounds like it could be a loose or worn alt. belt if it's just there when accelerating? Does it eventually fade off? Or go away when you take your foot off the gas? Or does it do it when turning the wheel?

Sorry, I guess I wasn't clear. The sound is not just there when accelerating. When I maintain a steady speed, the noise remains fairly constant.

No, the noise does not eventually fade off. It does not go away if I take my foot off the gas.

Sometimes the noise goes away if disengage the clutch and put the transmission in neutral, but usually not.

I haven't noticed any correlation with turning the wheel. It happens both when driving straight and when turning.

Wouldn't a belt correlate with engine rpms? As I accelerate from a stop, shifting from 1st, to 2nd, then 3rd, and 4th, then maintain a constant speed, the loudness of the noise correlates with the car speed, not engine rpms.

How old is your clutch bearing?

I don't know, but it's older than how long I've had the car. I've had it for 14 years and 75K miles. I haven't had to do anything to the clutch during that time.

This would be my primary suspect. I am surprised you are still on the same clutch.