You've probably got a very small hole in the condenser, which is mounted in front of the radiator. I expect a stone has hit it at some time.

System needs to be tested with nitrogen before being regassed. Sorry, I don't know any aircon people in your area.

Edited by Galaxy on 30/04/2015 at 12:07

It is usually the condensor that leaks.Very often around the lower support pillars that are not easily visible with the unit still attached to the water coolant rad.