Try it with the inlet/outlet at the bottom...and mount it so the tubing then goes down to the inlet on the pump.
With the inlet/outlet at the top the pump maybe getting air instead of water.
EDIT:Looking at the pic..turn the res round and use the port on the bottom of the res(the black part) for your outlet till pump and then use one of the side ports (on the black part) for the inlet till res.
Your res should be this way up in pic
http://www.frozencpu.com/products/69...tl=c97s165b145