But depending on how bad it is, just adding a can of gas every summer doesn’t seem like a bad solution.
Oh, you have the tree huggers running in circles yelling "ozone layer depletion, the world ends in 10 years!" On my Toyota - where hard aluminum cable parts joint there was a silicone/rubber O-ring plus the tightening nut bit. I had to replace to get a good seal. If its the flexible hydraulic line where it's crimped on - suspect like Stan said it needs a new cable -- or the end replaced (might be able to do on the car).