Kobelco SK25 hydraulic oil leak?

My SK25 excavator has sprung a leak.

The leak is on what appears to be an unused and capped flexible pipe as shown the photos below.

The leak is at the end of the white pipe where it meets the coupling going trhough the chassis and has the unused/capped outlet. The other two hoses, connected to the metal pipes inside, go to the boom.

Please can anyone advise what this pipe is for?

Thanks.

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Kobelco SK25 hydraulic oil leak?

Kobelco SK25 hydraulic oil leak?