Review on Universal Black A/C Valve Core Remover/Installer by MASTERCOOL - Model 58490 by Jeffrey Dunn

If you've ever had a leaking valve on an air conditioner, car or other, this is a must have. Replace valve. Don't let them ruin your valves in older systems. Often it is a valve that is leaking due to testing and a broken rubber seal. I had no problem removing the valves without losing coolant. There is a small part that you will lose, but we are talking about a small part. The pressure inside the device pushes the valve into the blocked area. Installing a valve exposes the unit to a small amount of air, but that's why dehumidifiers contain desiccants.