I never had much problem with those lids leaking, but, I left the fluid level slightly down rather then having it right up to the brim at the lowest point, and then I made sure the top of the master was dry, and the bottom surface of the rubber was dry. Those two things solved most of those leaking lid stories. If there was still a leak, I would check to be sure the top of the rubber and the bottom of the lid was also dry. If there is brake fluid between the metal and the rubber, you have created a void for more fluid to leak out, especially if the revivor is filled to the brim.