Clutch reservoir cap

Hi,

Am having to top up the clutch reservoir on my 2003 TD4 regularly, had a new master cylinder and no visible leaks so suspect will be needing a new slave cylinder soon.

Has anyone removed the membrane on the clutch cap to enable more of the reservoir capacity to be used, any idea of the function of the membrane, maybe to reduce the void and prevent hydrascopic action and moisture being absorbed from the ullage space??

Just curious as thought if I remove this would give me a greater capacity and reduce the period of topping up, make it a whole lot easier getting the cap back on without spilling fluid everywhere as well!!

Thanks in advance

The membrane is there to allow free movement of the fluid in and out of the master cylinder, without allowing air to come in contact with the fluid.