Where does the power steering fluid leak if there is no evidence of it anywhere. I need to refill it every week almost, not much, but it's always low. I checked the pump, (had it removed for a timing belt change) and there was nothing leaking from it.

 

I once had a piston seal leak inside the rack. Basically, it began filling up the air-space in the rack. Eventually, the rubber boots at each end of the rack filled up enough that I could feel what was happening.