How would I know if the power steering pump is bad or not
Start by checking the fluid level. You can test to see if the noise you are hearing is the PS pump by sitting still with the engine idling in gear, and turn the wheel left and right and listen to the pump noise, and see if it's the same noise you were hearing. It could have been that when you turn around to go in reverse and look out the back window you were turning the wheel slightly....? Just a thought...