Loud hissing sound when pressing the clutch pedal

[Kneale Brownson]

If there is no noise without touching the pedal and noise as soon as you do touch it, I'd bet on the throwout bearing.  Don't drive it till it fails because a throwout bearing can disintegrate and its parts can tear up the rest of the clutch/flywheel interface.
   
  The hiss will become a squeal, followed by a "bang" that can ruin the clutch actuating lever and damage the flywheel.   You'd be replacing the clutch anyway while in there to replace the throwout bearing, but you wouldn't necessarily have to replace other parts.

Andrew <elms88 at gmail.com> wrote:
  On 8/24/08, Huw Powell wrote:
>
> Sounds like it might be the throwout bearing on its way out?


Despite the hissing appearing even when I barely touch the clutch pedal?
Also, this would make it totally unrelated with the hydraulic problem that
the clutch seems to have as the clutch cylinder had air inside. Is it just a
mere coincidence?

Andrew