I just filled it up, it was making a nasty sound and it was on empty, but there are no black marks on the driveway when I park it. So it dosn't seem to be leaking. The only other option could be that it's being eaten or it only leaks when the car is on driving on the highway. What do you guys think? I got a new pump in September when the crank broke in on the inside and they had to change it.

 

Check your Coolant overflow tank!
Hope its not in there.

 

There could be a leak in the boot, or the power steering cooler (if equipped). The would dump ps fluid in the coolant. My best guess would be that the system wasn't bled when the pump was changed. Air in the system gave it a false level reading. Over time it equalized, and the pump went dry. Add fluid, then bleed the system if you want. You need an adapter from GM (basically a plug with a hole in it) and a hand vacuum pump. Pump and check the level until the level doesn't change.