Dan's Buttercake and Bill's re-Tort (grin)

["Eppinger.Michael" <Eppinger.Michael@domain.elided>]

Hey Dan and Bill,
The pressure between the lid (air gap above the gasket) and the fluid
(air gap below the gasket) is going to be the same.  This is regaurdless
of whether the cap is vented or sealed  (I think I actually have a
vented lid on mine).  The reasoning is that the gasket design is that it
is "folded" into itself.  So when you get a pressure differance between
the two sides of the gasket, the gasket will expand to equalize the
pressures.  This will continue until the gasket cannot expand anymore
(which you would have to be REAL low on brake fluid for this to happen.
I agree that the gasket's job is to minimize the exposure to air, of the
brake fluid.  If you fill up your master cylinder with brake fluid, and
put the gasket on, the fluid will absorb some moisture out of that
trapped air.  But if it is sealed, you will not introduce new (wetter
air) into the system, so it will limit the amount of absorbsion. 
Just my $0.02 worth.

Epp
(who also wants a piece of buttercake)