Bipolarcivic

i have a 93 civic sedan and i keep loosing break fluid out the back of the master. so im about to put the second one on ( both are good) and was wondering with the master off where it bolts to the power booster is it suspost to have suction there? i bought a new booster and it dose it to. have i miss something or what? note both masters are new and i have a new booster.