For a few months a screeching noise likened to dragging your fingernails over a chalk board has been comming from my engine bay...

I posted about this a few weeks ago..... and tried the good advice recieved, but the horrible noise is still there, and is takes 2 minutes of run time to start happening

It is NOT...
*Not the clutch, as it does it some times when the engine is comming down in revs out of gear or between gear changes - up or down.
*Not the little fan in the fuse box next to the battery, as i've popped a lolly stick in the fan blades and stopped this fan, not this either.
*Not the blower on the front of the engine, as I stripped this, cleaned the brushes, changed the bearings and re-assembled = even removed the device completely from the vehicle - still screeches..

Have pondered that is may be a resonant sound from somthing triggered by engine vibration that will change dependant on engine load or acceleration/decelleration.... maybe....possibly....

I'm at a loss now...

Generally the screech occurs at minute throttling above cruise, in any gear, some times on decelleration, and some times continues a while but quieter when the vehicle is stationary and out of gear too...

the noise increases dramatically when minor throttling is applied in any gear... however not enough throttle to accelerate at any rate will still produce the screech, and when the vehicle has run for say 30 minutes or more the screech is always there but changes slightly as power or revs or speed change... though not always predictable.....

So, it's NOT necessarily engine load or rev speed increase related, NOT gear related or clutch related....
Its NOT the main radiator cooling fan either...

The engine belt pulley bearings are all recently new, belt does not slip and is dry

I'm wondering about an air leak of vacuum or pressure some where past a hot rubber pipe, creating the sound when you can
(humour me here) blow past a piece of grass between your thumbs and make a squawk sound....
Maybe its a blow-past a pipe some place ???

Any one got any clues, as this noise is an embarrasment from a car like this in town...

HELP PLEASE......

Regards to all
Grant