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post #1 of (permalink) Old 08-22-2009, 09:04 AM Thread Starter
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Thumbs up Leaking Master Cylinder Cover

I have a three year old reman NAPA Master Cylinder on my 85 CJ. Break fluid from time-time weeps out from the front half of the cover from best I can tell. The rubber gasket is clean and there is no dirt or debris on the rim of the cast master cylinder itself. Any suggestions on how to stop or do I have to replace the entire master cylinder? Thank you for your input.

1985 CJ with a transplanted 94YJ 4.0L motor, T176 tranny, mainly stock otherwise. ><>
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post #2 of (permalink) Old 08-23-2009, 08:06 AM
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Check the cover to see if its not warped somehow, take a piece of steel, I keep a 1" thick piece around just to check items that can warp. Anyway lay the cover on it to see if it meets the surface of the master cylinder flat, it could be bent/warped, from what I have no idea but that can be one way of checking it, yeah, yeah I know it has a lip on it but you should be able to check it anyway and the edges of the master cylinder have to be super clean. Pull the gasket out of the top and clean all the rust, whatever out of there, could be something behind there to leave a gap in the top, just enough to let fluid leak by. Hope this helps.


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post #3 of (permalink) Old 08-23-2009, 11:51 AM
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Assuming you have a metal cap not plastic;
yes, they get bent/twisted/warped on the way to the re-manufacturer. They get cleaned & painted but not checked for an exact fit.

If you can find/see where it's leaking at .... a little tweeking with a block of wood (or ??) and a hammer usually does the trick.

Check the 'hold down' clip, sometimes it's not putting even pressure on both ends/sides of the cap. It gets bent up just like the caps. Adjust as needed.

Also check the gasket ..... sometimes they are malformed and will not seal properly.

If it's a plastic cap ................ find another one.
Good luck

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Last edited by GoldToyBox; 08-23-2009 at 11:54 AM. Reason: correct spelling & add more info
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