My dad needs some help with his 1987 Toyota Cressida. He's taken it to
several mechanics, and no one has yet found a problem:

"It emits a moaning sound  sometimes
when starting the engine and it goes away after
several seconds, Seems to have nothing to do with the
revolutions of the engine because it remains constant
when  feeding the gas.

It doesn't do it every time and sometimes won't appear
for a day or so. Never happens when the car is running
and the wheels are turning-very infrequently it will
happen when the car has stopped at a light and gas is
fed  to get going .

As close as I can describe the sound is that it is
similar to that created when blowing across the top of
an opened coke bottle."

Any ideas would be appreciated!
Thanks