i would start by checking if you have any fluid in your power steering reservoir ,it is cheaper in the long run to replace than repair because if you repair you will find there will be more labour involved and that is only if you can get a repair kit,i work for a vauxhall specialist and we generally replace.
i hope this helps you,craig
i had the same problem with my daughters 1.8 zafira a , told new rack ,
i thought i would give the steering rack a dose of LUCAS steering rack
oil repiar.. got some on ebay.. removed the power steering filler cap
and added slowly turning steering left and right to get rid of any
bubbles... i had my doubts,,, so i filled the rack , degressed
underneath so i could see if there was any leaks,,, took her out for a
long drive steering smooth as butter,,,, good i thought so i placed a
old white towl underneath left over night no drips no runs
perfect ever since.. i think what had happen on this rack was it was
running low and got very hot breaking down the original oil.. the
viscosity of the lucas oil is very think, i noticed the old oil came to
the top of the cap light pink and watery. so could have been that, im
just saying worth a try...