Pressure relief valve in cap, checking

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Fig 1: Checking Pressure Relief Valve In Filler Cap

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Position cooling system tester V.A.G 1274 with adapter V.A.G 1274/9 on cap.
Generate a positive pressure using hand pump of cooling system tester.

Pressure release valve must open at a positive pressure of 1.4 to 1.6 bar.

If check-valve does not open as indicated:

Replace cap.