zafira gsi 2004 z20letbubbling expansion tank and white smoke puffing out the back of tail pipe!and myheater is cold! temp guage normal/ runs fine no problems! no lose of coolant/no water in oil/ no oil in coolant!!! been for a drive and the pipes coming off the rad are presurised is this the norm? and theres lots of preasure in expansion tank!recent vxr turbo.could this be head gasket? or water pump problem?