Check your Power steering lines especially where they may clip to a plastic holder on the frame. Water and salt spray like to corrode the line at these points. Sometimes you may need to disconnect the line and take it off and test it for pressure holding capability.
Make sure you use the correct fluid for your Brand. Sometimes the vanes inside the pump wear, especially if it ran dry. Then the unit will need to be replaced.
Last, when steering pivots, like balljoints wear, they cause more drag making the unit to work harder to steer. The pump can squeal under the added resistance.