I have an external liquid cooling setup which has been running for about 2 years. Every month I have to add about 1 to 2 ounces of coolant and there are no leaks. When I put the system together I purged all of the air so there isn't anywhere for it to go. I took the cover off the external unit and inspected everything with a magnifying glass and without while everything is running. I also took the cover off the computer and inspected. I took pieces of paper towel and put them in strategic places where there are joints and also under the radiator. The tubing runs from the external unit to the inside of the computer with quick releases in the middle which I also wrapped with paper towel. It is about a month now since I topped off the reservoir and I am again short between 1 and 2 ounces of coolant and there are no indications of leaks on the paper towel areas. I am using UV reactive green coolant and I have also used a UV light to inspect the paper towel areas and nothing has leaked. What a mystery! If anyone has an idea I would really appreciate any feedback or knowledge about this problem. I have two other liquid cooled machines and they don't lose any coolant, not a drop.