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maybe the o-rings from the Bleeder Valve ( 99610634702 ) are leaking. Best to test by making the collection container dry and if the engine is warm to see if it is leaking at the bottom.

https://www.rosepassion.com/en/diagrams-porsche-cayman-987c-2-2012-eu-cayman-2-9-pdk-gearbox/engine-and-fuel-feed-36/expansion-vessel-expansion-vessel-plug-5192/99610634702-p117808-bleeder-valve-99610634700-99610634701-117808