There a a wide variety of possibilities: pump,rack,pressure hose, return hose, reservior are your main components. Fill the system up, have someone turn the wheel back and forth while you look for obvious leakage. If none, hold the wheel sharply for short bursts while you look. If still nothing, get some dye and add to it and check every 10 miles until you see it. If all else fails let a real mechanic fix it for you.
If the reservoir keeps losing fluid.
Check power steering fluid first, then take it to the shop if it is full.
Faulty power steering pump, bad power steering fluid, insufficient or excessive power steering fluid.
you may need more power steering fluid.
Air in a power steering system is caused by low fluid or a leaking seal. When the fluid is low, the pump becomes exposed to the air and causes large bubbles to form.
Low on power steering fluid. Loose or missing drive belt. Faulty power steering pump. Faulty power steering box.
Assuming you have power steering, you may have a loose belt or the power steering system has a leak and the power steering fluid reservoir is low or empty.
Low Power Steering Fluid
your pump could be low on power steering fluid, your power steering belt could have came off if equiped with a separate belt and finally the pump could have failed from low fluid, or dirty fluid
It is most likely going to be the power steering fluid. Usually when your power steering fluid is low, the car will make a groaning or whining sound. Hope this helps!
Low fluid and dirty fluids.
Check your power steering fluid.