hi , i have a 97 imprezza wrx 2.0T jdm . I am losing water from the the expansion tank and also constant air bubbles in header tank when reving , i only seem to lose water when im giving it a bit , it looks like im only losing the coolant in header tank as i only have to top up a litre or so, I have tried draining the cooling system quite a few times and refilled system many different ways.. how can air be getting into the system constantly?? local garage done a sniff test for free and said they dont think its head..... we leaned toward header tank cap(old wone was worn) ... replaced and still have water bubbling in expansion and still losing water maybe slightly better than before though. any help would be much apreciated