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?



From your question, the whine is linked into braking both when the veicle is stopped or moving. I would first look at the brake servo, its hoses and valves. A vacuum leak can give a whining like noise.

  • Also called the power brake booster, it has the master cylinder bolted to the front of it and mounts to the firewall. – mikes Nov 22 '13 at 23:24

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