7858523 Radiator Test Cap (Late Model Audi, VW, Porsche) Astro Pneumatic No. 23The 7858523 Radiator Test Cap (Late Model Audi, VW, Porsche) Astro Pneumatic No. 23 allows easy testing for leakage in radiator system and quick change of coolant. Unit is suitable for late model Audi, Volkswagen & Porsche vehicles. The 7858523 Radiator Test Cap (Late Model Audi, VW, Porsche) Astro Pneumatic No. 23 works with the 78585 Astro Pneumatic Universal Radiator Pressure Tester & Vacuum Type Cooling System Kit.