Over the past three days we have been slowly increasing GN2 heater power on CP4 via new variac. Attached is plot since Wed. with variac settings. Today I opened the LN2 draw valve all the way (2-1/8 turns) at Dewar to increase flow but as we know from last time, we bottom out and need the help of the pressure build circuit. I opened that valve 1/2 turn and slowly the Dewar head pressure increased from 12 psig to 16 psig, but I noticed a hissing and vapor coming out of the capped pipe where the LN2 delivery truck connects to. My guess is either the top or bottom fill valves is leaking. I closed the pressure build valve for the weekend. The temperature dip at the end of the plot is likely due to intermediate increased flow and is now recovering. Will monitor over weekend.