Jim Yanik wrote:
> "duckbill" <ltcauth13@nospam.cs.com> wrote in
> news:47a59dcb2be108e0cbed856546008470@localhost.ta lkaboutautos.com:
>
>
>>Elle, what you said makes perfect sense, except I never let that big
>>master cylinder get below half full. When bleeding the brakes with a
>>short stroke, because of the wood, I was especially careful not to
>>introduce air. At that point, I only thought I had air in my system.
>>I thought I may have introduced air months ago when I used a one
>>person brake bleed setup. Never got any air during the bleed. This
>>time there were two of us doing the bleed. When It went to floor, I
>>thought this could not be possible. Fluid level was fine and by
>>continuing to pump the brakes, pedal came up and then we lost it
>>again. Yes, I have also introduced air into a brake system before on
>>a different car by letting reservior get too low. Did not want to
>>repeat that mistake when I was trying to get air out of the brake
>>lines. Thanks for your input.
>>
>>
>
>
> If the master cylinder piston seals fail,fluid seeps around the seal
> instead of being pushed into the brake lines,thus the pedal moves,but no
> braking;bacause no pressure is applied to the hydraulic fluid.
> I've read that moisture can cause corrosion in the aluminum MC bore and
> that erodes the seals(neoprene?),affecting both sides of the system.
>

the best explanation of the system is here:

http://www.tegger.com/hondafaq/maste.../howworks.html

[the rod inside the item labeled "second circuit return spring" is not a
fixed rod so only hydraulic pressure moved the fist circuit piston, not
mechanical.]

there's not really a "both sides" - they both draw fluid from a common
reservoir. the rubber's not affected by water. water contaminated
fluid however does set up differential corrosion between the steep
pistons and aluminum bore which in turn can abrade the rubber, and
contaminated fluid from oil vapor, etc can affect the rubber... but
it's all academic. keep the system regularly flushed, and
replace/re-seal every 10 years and you'll be fine.

[i have 17 years on my 89, and i think it's only now thinking of flaking
out.]