Loud hissing sound when pressing the clutch pedal

[Andrew]

Hi folks,

Greetings from a returning old-timer of this list. I was an active member of
an old q-list about 10 years ago but uns*bscribed when I had to part with my
beloved 4kq. Now, I have a technical question not exactly about an Audi but
still Audi-related.

My 1999 Passat 1.8 T, is in many ways similar to an A4 and perhaps some of
the list gurus could help me out.

It first started with a clutch pedal not returning all the way up after
being released. So, I had to push up it with the toe. The brakes beeding was
long overdue anyway, so I bled the brakes and the clutch and the pedal now
goes all the way up. However, there is now some loud hissing or whistling
sound heard when I press on the clutch pedal. I would describe the sound to
be similar to hissing of the worn-out belt. Except it clearly comes from the
rear (not the front) of the engine. So, it cannot be a belt. The sounds
starts to be heard as soon as I press the clutch pedal only slightly and
gets louder when I press it all the way. IIRC, the hissing, although less
loud, was there before the bleeding but now it is totally outrageous.

I suppose these may be a very well known symptom but having very little
experience myself with this type of car, I am asking here for an advise. Any
suggestions would be greatly appreciated.

Cheers,
Andrew