I'm driving a manual 96 Toytota T100, and recently the engine started making a high pitched, almost inaudible whine. Some things I've loosely figured out:
- It always stops when the brakes are applied, but doesn't stop for the clutch
- It seems independent of speed or revs
- It sounds cyclical with a slight random component, and fades in and out as I'm driving or stopped, but will usually go for 30 seconds at a time
- It seems independent of the heat/ac fan speed
- It seems temperature independent (both outdoors, and how long the truck has been running)
Any ideas where to start looking for the problem?