Power steering ?

My question is regarding my 89 wagon with 307 vin Y engine.
The power steering pump seems to be whining at idle.
When i am stopped at a light, i hear a slight whine and can feel a little vibration of sorts through the steering wheel. If i turn the wheel slightly the noise goes away.
I drained about 6oz's of ps fluid out and replaced with 6oz's of Lucas ps fluid but that did not seem to help.
Is my ps pump going south ? or should i completely drain and replace the fluid first to see if that fixes the problem.
Any suggestions would be helpful.

Thanks

Al

If you want to change the pump, they're fairly inexpensive to replace. You'd need a power steering pump pulley puller though. Wow, that can be a tongue twister.