Brake / Clutch Fluid Reservoir Diaphragm

[Our Gee]

This is just a general query and not related to a problem, so here goes. Does anyone know what is the purpose of the Brake and Clutch Reservoir "Diaphragm". Apart from forming a gasket seal between the metal cap and the plastic reservoir is there another purpose. The shape does seem to be very complicated if indeed it is just a gasket and why is there always what looks like water condensation droplets present ?. Thanks.

[Stu]

You have just answered your own question


Without that diaphragm where do you think that water is going to go? Straight in to the brake fluid

[Sullivj]

It's supposed to keep the water out, but mine failed and the fluid became 'murky'. 


I had the reservoir cleaned out, fluid replaced and flushed through and a new diaphragm and cap fitted. 


The new diaphragm was firmer than the old one.  Maybe yours would also benefit from replacement.