finger crossed...g13b is not that fragile.....how was it running? missing? loss of power? any issue in starting?
park the car on inclined surface...with engine on the higher side...then start the car and top up water...u can press upper hose pipe a couple of time to make it burppp... also observe if water is violently jumping out of radiator after heating up a bit...
replace the cap...use correct spec, check if it 0.9 bar or 1.1?
fill up the expansion valve till max point and observe it it reduces water...
exercise caution for above procedure and if u dont know wat u r doing then let someone else do it for you!!