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Hello all,

I recently began the rebuild of my brake master cylinder. After getting my unit disassembled, I noticed a couple differences between what I have and what came in the kit. In the picture, the old piston is on the left, replacement on the right. You can see that the replacement has a copper disk covering the holes; I presume to act as a one way valve. Is this ok? Also, the kit came with a relatively thick rubber washer, as seen between the two pistons. My master cylinder didn't have a corresponding washer. Where does it go? Thanks for the insight in advance!

-Mark

P.S. - that rebuild kit is from rockauto.com, listed for $12.08 right now...Kanter wants $12 just for the dust boot/bellow!

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Be careful with Rockauto parts, good price, but may not be correct parts in box. I have had to return some because the wrong parts in box.
Wes

For the 1" master cylinder, I have been using Napa UP2 rebuild kit for years. Parts look similar.

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The thick rubber washer is the first item to go into the cylinder and rests in the outlet end. It seals the check valve to the cylinder body when the spring pushes against that. Chances are your old one is still lurking in there and you will have to pull it out with a hook.

Thanks for the comments, especially the bit about the rubber washer, Ross. Wes, I've had the same issues with them before as well, which can be very frustrating, and the main reason I figured I'd ask the experts here! And good to know that Napa carries the kit as well.

Any comments on the copper disk on the piston?

I'm sure it will need to be honed out, and that it's been honed before... what's the maximum inner diameter for the bore?

If you find it is too worn to be serviceable after honing, brand new masters from Kanter may be a better approach than sleeving.

I'm thinking the repair manuals only allowed something like .004 of an inch for honing on a wheel cylinder or master cylinder.....
John

OD - I apologise for the bluntness, but why? It looks like brass or stainless steel are used for sleeving, which would eliminate the corrosion concern. The cost of sleeving looks cheaper than what Kanter is asking as well. Is there another factor I am overlooking?

John - thank you for that, I would have thought it would be a greater tolerance.

Perhaps it was bad information but several folks have told me that a brand new master cylinder with guarantee was only a couple of $ more than sleeving.

Usually if they are pitted much at all you can't get them honed out. Don't quote me on the .004, but that seems to be what I remember.....
John