Its showing hot on the gauge think ive turned it off before its got to the stage of boiling out of the expansion tank. I roughly no how to drill it, was just going to get a new one anyway as they are not expensive. My concern is does the whole thermostat housing have to come of or can i split it in position ? Ive got roller barrels and it makes hard to access it i struggled to get the new bypass hose on nearly dislocating my thumb lol. Also if i have to remove the full housing it will need a new o ring which i could order ready. When you split the housing does the thermostat have a rubber seal on it or is it another o ring i will need to get ?