<VV> "sealed" master cylinders

[Chris & Bill Strickland]

okay, a couple folks have caught me, they think, on the idea that master 
cylinders are vented (or not) to the atmosphere, because some of them 
have the rubber diaphragm 'follower' sealing the master cylinder cover.

well, maybe that is how it is supposed to work, but this is Virtual 
Vair, so we are talking about Corvairs, all Corvairs, and I know that 
the 60 passenger models and the early fc's were directly vented. okay, 
some of them do have the seals, or should have them, but again, we are 
talking Corvair -- oem, they all have a cast iron master cylinder with 
an 'as cast' sealing surface, and of those with the sealing diaphragm, 
nearly all of them have some corrosion (rust) on the surface where that 
diaphragm is supposed to seal. if it is even slightly rusty (or if the 
seal is old and stiff or has rust flakes imbedded in it), it is not an 
airtight seal. end of story -- it sucks and vents.

I think road splash is potentially a serious problem for those vented 
early fc master cylinders and for any other vehicle with under the floor 
or frame mounted master cylinders.

also, it has been mentioned that the wheel cylinders and cups 
deteriorate over time with just mechanical wear, if nothing else, and 
you can suck all sorts of air, crap, and debris (all potentially 
containing moisture) past the cups when the brakes return to the 
un-applied condition -- a minor, imo, contamination, but still a 
possible source of  contaminated brake fluid.  I think it is just as 
likely, if not more so, to happen on the application phase -- keep those 
dust boots in good condition.  more reasons to flush every so often -- 
racers do it routinely, frequently, & religiously.

Y'all Drive On now, yeh he'ar,

Bill