When I start my 91 (syncro Westy) up I get a real SCREECH
from the back. When I go back there and take off the engine
lid, I think it is coming from the alternator (I only have
the alternator, water pump and main pulley - NO air and no
power steering pulleys) .  This SCREECH lasts about 30
seconds and then no problem while driving until I let the
van sit  a bit then start it up, then another 30 seconds of
SCREECH.

I changed the belt (the old belt was OK) and I still get the
SCREECH.  There is not too much tension on the belt, if
anything, the belt  is a bit loose (I just tightened it
hand tight).  When I pore some water on the belt and pulley,
the SCREECH  goes away.

Does this mean that the alternator is about to give out, or
is it just a recalcitrant belt and pulley, or should I
tighten the belt???

Thanks,  Malcolm