[elk hunter]

it is possible that the master cylinder still has air in it, and yes you should have the master as level as possible air rises to the highest point which would be the nose of the master cylinder. the wheel cylinder may not leak fluid because the fluid is pushing on the inside of a conical shaped plunger which expands the sealwhen pressurized. when the fluid returns the seal is relaxed so it is possible that that one wheel cylinder is sucking air. i would recomend replacing wheel cylinders in pairs. the normal measurment on a brake drum for the maximum size is .060 over the measurment from new. this would be something like a 12" drum would be good to a maximum of 12.060", and should be cast on the drum on the outside face around the rim. the master always has air above the fluid so no the cap seal is not the problem. you also should not pump the pedal too quickly because that causes the fluid to foam which puts air in the system. nice and slow. you can diagnose where the air is at by clamping the rubber lines (all of them) and push on the pedal. this will tell you if the air is in the master. if pedal is solid, release each clamp one at a time to reveal where the air is. if you cant get the air out most shops have either a pressure bleeder or a vacuum bleeder.