An old pump or power steering box will have harbored lots of sediment and years of dirt etc.. you need to flush it ALL..... this new power steering pump being a bit stronger too...
and it will push that old slug, dirt and debris straight into this new one.. and control valves or power cylinders stuffing it. Causing failure and voiding warranty.
Results of not doing this...people buy a POWER STEERING PUMP or box.. then a pretty immediate failure with a call of... "power steering pumps faulty" comes the claim.
Well.. YES it is NOW...but could that have been prevented...? 
It does not matter if your buying the Pump from us or GM Detroit / 711 etc.. the same guidance is needed.. except most suppliers will not sorta nag about this aspect.. but its to help you not nag - you incase its just not known. Nobody knows everything.
.. all these parts while never fail safe 101%... nor are most of the novice repairers...consider these are factory pretested to work under pressure.. ..they come wrapped . PS fluid residue's often in the bags its come in .... because they have been tested.
CLEAN OUT ALL THE FLUID AND CRAP first before installing a new pump or box .. flush it.. like you would a radiator.. don't kill off good parts by cutting corners. You can install inline filters too if you wish to prolong the life of hydraulics like these parts.
Early GM PS control valve and cylinders as found in 58-82 Corvettes and 58-64 Full Size Impala & Belair, Parisiennes, Laurentian need the same help.
If installing on a car that has been sitting, it is advisable to install a filter inline before valve, or change the pump as well.
