Is your whine more pronounced cold or hot? Do you see any signs of the ps fluid being airated?? "frothy foamy look" to it?

I have a 190E with a whine which is the pump in the transmission. The hose trick is good for finding this as would be a LOOOOOOOONG screwdriver or wooden dowel. Just place it on the bell housing and see if it's louder there, or under car. You can also check the alternator too, but usually when mine has been ready to give out. .its a high pitched squeal from the brushes being almost worn completely down to nothing.