Master cylinder still usable?

Gene Heagney · Posted: Mon Dec 10, 2012 7:01 pm Post subject: Master cylinder still usable?

I took apart my freeline master cylinder to put new seals in it, as well as to sand down the piston a little because it was sticking. In the process I put a couple small nicks in the cylinder. I did it the stupid way. I know I should have used air to force the piston out, but I didn't think it would be that stuck (maybe an expensive lesson...).
Anyway, what are your suggestions or opinions. Should I sand it down/hone it a little, put it back together and give it a try. Is there anything else I can try to help make sure the o-ring's seal? The nicks are deep enough that I don't think I will be able to hone them out, but maybe enough to help the o-ring seal? Also the pison for this has two o-rings, far enough apart that one would always make a seal.

Tyson Henry · Posted: Mon Dec 10, 2012 7:28 pm Post subject:

Personally, I wouldnt sand it at all. No sense in making the bore larger and taking away the anodizing if its not going to get sanded all the way out anyway. And, like you said, there are two seals so theoretically it should still hold good pressure. Might have some slight leakage over time though.

If it doesn't work, going to have to buy a new master cylinder (maybe you can source just the body). If you have to replace I hear the MCP billet ones are great.

Walt Gifford · Posted: Tue Dec 11, 2012 8:02 am Post subject:

Why do people think sandpaper will smooth out a highly polished and anodized aluminum bore? I've seen more guys ruin things trying to fix them. Just flush it out with some brake clean and a tooth brush. If it's all scratched up for some reason, you can very lightly hone it for 2 seconds to take off the high metal as a last ditch effort to get some more mileage out of it but, if the scratches are excessive or corrosion has et through the anodizing it's pretty much junk.

The bore in the picture looks fine just put it back together with some high temp brake grease on all parts.

Gif Cool

_________________
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Gene Heagney · Posted: Tue Dec 11, 2012 10:30 am Post subject:

I don't think sandpaper will smooth out a highly polished anodized bore. But it might knock down any jagged or raised edges.... That was my thought process.
Thanks for the advice though. I figured I would just give it a coat of high temp grease, especially where the nicks are, then let the seals smooth it out during reassembly. I'll put it back together and give it a try and see what happens...

Tim Salvino · Joined: 20 Nov 2010 Posts: 257

Ive had bores MUCH worse than that (anodizing completely worn through) and once assembled, they worked fine. One worked exceptionally well. That said, they didnt have any big nicks or anything, just a worn surface.

I would put it all back together and give it a shot. Remember, the piston doesnt move much at all once it's all together. Maybe 1".