WARNING: This page is about a different car, the 2006 Volkswagen Jetta and 2005 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.
-- Position cooling system tester V.A.G 1274 with adapter V.A.G 1274/9 on cap.
Fig 1: Attaching Cooling System Tester V.A.G 1274 With Adapter V.A.G 1274/9 On Sealing Cap
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
-- Operate hand pump.
The pressure release valve must open at 1.4 to 1.6 bar.