Steve:
Guess my prose is not up to par.... I agree that the fluid leaks from
worn/torn rubber hydraulic seals in the aluminum body and this fluid gets
sucked into vacuum cylinder. I have found that brake booster "stickiness
problems" are due to corrosion in the vacuum cylinder.
My suggestion only address the vacuum cylinder problems. One should properly
replace the hydraulic seals and possibly sleeve the bore as part of a
booster rebuild (I have rebuilt at least 7 boosters and never had to sleeve
the bore).
Incidentally, I use silicon grease to lubricate the leather vacuum piston
seal.
Wayne
-----Original Message-----
Wayne,
While I have no issue with your suggestions on a smooth vacuum canister,
the leak past the leather seal between the canister walls and the large
piston is NOT the reason for loss of fluid. It might be the reason for
low pressure differential across the disc that is driving the boost.
The seal that leaks is the small one ( ~ 5/8 diameter) in the cast
hydraulic cylinder and the long shaft attached to the canister piston.
This is the final barrier between the fluid and the vacuum differential
across the large piston. Once the hydraulic fluid gets past that shaft
seal, it will fill eventually fill the large canister on the hydraulics
side, or perhaps by-pass the leather seal into the intake manifold (and
out the exhaust). The damage was done back at the push rod seal on the
way out of the hydraulic cylinders.
Doesn't hurt to make the canister nice, but that is not the prime
failure for fluid loss. Shouldn't be any either side of the piston, anyway.
Steve
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