teflon paste seals better than the tape but that is for NPT, not needed in your app. it should seal by being tightened a reasonable amt & if not either the male or the female threads are fubared. If this is a banjo fitting it might be leaking at the copper washers, one on each side of the banjo fitting & the ribbed OE ones (even a used pair) seal better than the smooth replacement ones. New ribbed ones ain't available to my knowledge.