When performing retrofits on older R-12 equipped air conditioning systems, we would occasionally encounter damaged or broken Schrader valves. When the top portion of the Schrader breaks off in the service port, the section that's left behind resembles a hollow barrel. They are difficult to remove since there is nothing to grab a hold of.
Rather than scrap the part, a T15 TORX driver can be used to extract the barrel. With a light tap, the teeth on the driver bite in to grip the soft brass of the broken Schrader valve.
Be sure that system pressure is relieved before attempting to remove Schrader valves from an air conditiong system.
Always wear safety glasses when working with hand tools
Always wear personal protective equipment when working on air conditioning systems.