Checking function of cap:

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Detach rubber (1) from special tool 17 0 002.

Fig 1: Detaching Rubber From Special Tool 17 0 002

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Fit special tool 17 0 007/17 0 008.

Screw cap (1) onto special tool 17 0 007.

Fig 2: Screwing Cap Onto Special Tool

Courtesy of BMW OF NORTH AMERICA, INC.

Pressure relief valve must open between 1.65 and 2.2 bar.

Build up pressure with special tool 17 0 002 and watch pressure gauge to ascertain when opening pressure is reached. Note down measured opening pressure.

After a waiting period of approx. 30 seconds, the pressure must no longer drop by more than 0.4 bar below the measured opening pressure.