if ur steering rack leaking, then send it for overhaul.
if ur steering really hard to steer or at time squeking noise occured, check ur PS fluid, PS pump, replace if neccesary..
last time my e30 with m40 engine & the steering so hard to turn, some people advise me to replace the rack, some people advise me to replace the pump.
recently i converted to m20 engine, using back the old rack, pump come together with the m20 engine, now i feel much much more easier to turn compare to last time. much more lighter..
Too dirty power steering fluid will cause your power steering rack malfunction one or both side becoz it clog up the circuit inside.
Hope this help.