Fritz1 Posted November 28 Report Posted November 28 got pilot and copilot master cylinders out to fix spongy brakes once for all, no fluid leaks whatsoever, one pilot master is showing a small amount of scoring in the bore, aluminum piston must have contacted bore, have one set of spares that have better looking bores, a new master cylinder is about $3800 which is kinda stiff, trying to avoid that Dumb question: Is there any Cleveland spec stating how much scoring is permissible in the bore and how do you measure it?? I have used LASAR rebuild O-ring kits before, think $15, but they are not answering their phones today, same kit at MC Farlane is $38, so these kits are inexpensive and available. Has anybody used a Marsh Brothers M-00-1003-1 rebuild kit? it is about $200, appears to have better piston rod seal, does this really seal better against air creeping into the masters?
Yetti Posted November 30 Report Posted November 30 scoring is what allows air to creep. If you search around here I think there is alternative master cylinder that is the same spec.
MikeOH Posted November 30 Report Posted November 30 I have honed out minor scoring on automotive master and wheel cylinders; no idea if that is acceptable, or what the limits are before the piston cup won't seal, for aircraft. Seems low risk to try, BWTHDIK
PT20J Posted November 30 Report Posted November 30 How deep is the scoring? Can you catch it with an angled pick? If it is minor, I'd leave it alone and just replace the o-rings. The cylinder is sealed and full of fluid so the only way air is going to get in is around the piston rod seal.
Fritz1 Posted November 30 Author Report Posted November 30 have six masters, best ones go on pilot side, next best set goes on copilot side, two with the worst scoring will get discarded, the weak spot of these cylinders appears to be the shaft seal, the piston is supported in the bore exclusively by its O-ring, any side loads on the shaft loads the shaft O-ring which only has so much flex before air moves in, the Marsh STC kit has a lip seal for the the piston rod, which should be better able to seal and follow a piston rod that moves sideways, will call Marsh on Monday to see what they have to say for their product and if they might know service limits for the Cleveland 10-24D
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