Brake master cylinder leaking

[Battson]

My right brake master cylinder has been leaking fluid out of the main piston's seal, where the shaft exits, for some time now.
It's a very slow leak, and the fluid loss is not significant at all - just annoying. Brake fluid is nasty aggressive stuff.

Does anyone have any suggestions on how this could be fixed?? I will be draining the brake system next weekend.

[marcusofcotton]

What are you using for brake fluid? I hope not automotive type. Some use ATF but 5606 is very reasonable, common for the purpose in airplanes, and great viscosity properties (stays thin in the cold).

Mark J
NE MN

[Battson]

I am pretty sure it's MIL 5606? Either that or some other MIL-spec fluid.

[Mark Goldberg]

Jonathan, if you are using the Gerdes master cylinders we sell I have some o rings for them that would probably solve your problem. Mark

[Battson]

Hi Mark,
Yes I am using the Gerdes cylinders which I bought with the kit. If they are standard sized o-rings I can probably find some here. If they are pretty unique, I should buy a set.

[Mark Goldberg]

Just wanted to post an update on the Gerdes new/surplus master cylinders we sell. Recently, we started going through them all, polishing out any corrosion on the bore and shaft, and installing new orings. This should eliminate the few problems we have seen like them leaking or the shaft not returning all the way up after braking. Basically overhauling them. This costs $15 per cylinder so the price went up that amount. But all in all it should be helpful. Mark

[Battson]

I can attest to the fact that they work a whole lot better with new hardware installed on the inside.

Mine have never been better, since I disassembled them and change the internals. Thanks for the parts, Mark.

[N942VT]

Same here, Mark set me up with new O rings and all is good - Thanks Mark