[georgevan]

This kind of problem has occured to us several times,with older BMW´s.
(150.000 kms about)
The problem is dirth collected on the rotor from the carbon brushes of the fan motor.
It is a small dark layer on the copper rotor.
After removing this discolouring,carefully,with very fine grinding paper,the squealing will be over.
(Seldom reason of squealing are bearings.I have never experienced this))
It needs a little more knowledge of engineering,to do this reparation.
And you must take your time....
The lifting out of the fan with motor will not be too difficult.(However..???)

The removal of the metal end cover of the electro motor must be done with the right amount of power. It is pressed in place by steel holders.
I use chisel and hammer,and pliers.Carefull,as mentioned...!!!
Than I take the coal brushes off the rotor,and with long strips of grinding paper (30 cm x 6 mm ),I clean the copper surface.
Surely dust has collected inside the motor,which can be removed with electro clean.
Reassemble parts,
(Push fan little in motor direction,otherwise coal brushes don´t reach rotor) and put steel cover plate in place.
Hammer steel holders,so cover plate stays firm in place.

I did this reparation several times,and only last time I was not sure,if operation succeeded,as I wanted,because the copper rotor was deeply scratched.
Am available,to provide further specific information.Fr.gr.George