Drama tonight, long story short it was the cpu block. It was completely and utterly bunged up. Bits of oring mixed with what i can only describe as tissue paper. Weird... anyway rebuilt the block (alphacool XPX acrylic block), filled the loop and... disaster! The block leaks! Immediately took it apart and thankfully only a few drips onto the m.2 slot (dont worry, nothing was damaged). Checked the block, cant see why it would be leaking. Orings are in place and making contact. Did a simple test, filled the block with water and plugged it. Shook the block vigorously and still leaking. Can see water coming out where the block and acrylic meet which means the oring has failed. On further inspection i could see the oring isnt even making contact on one side. Oring looks fine though so maybe acrylic is damaged.
anyway whipped out the old bitspower block as temporary replacement. Looking at getting aquacomputers Kryo rgbpx block next. Abit disappointed with the alphacool block tbh.
new flow rate is as follows
3.89 L/M
Excellent!