S13 Water Pump – Most JDM SR20DET’s have been sitting in junkyards in Japan for years.  Old water pumps have a tendancy to seize and it is recommended to replace it with your complete motor refresh.  It is also recommended to replace the Timing Components, Gaskets, and Timing Components.
 
Part #B1010-52F01
 
Other items you may want to consider:
S13 Full Gasket Kit
S13 SR20DET Oil Pump
S13 Oil Pan
SR20DET Timing Kit