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Master cylinder- rebuild or replace?

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Scott R View Drop Down
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    Posted: 06 May 2007 at 10:38am

Never done a master cylinder rebuild before, but always willing to explore the unknown. Would like to know from those that have been there done that… is the cost, time, trouble worth rebuilding vs. just buying a new one?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bluax Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2007 at 10:44am
If I can do it, ANYBODY can do it!  and I've done it at least 4 or 5 times and have now even graduated up to rebuilding fuel pumps.   Degree of success on the master cylinder can, however, depend on the bore wear.  When disassembling just lay the parts out in order (assuming it was working before, if not, its a fairly logical system).
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote F Bill Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2007 at 3:43pm
If you can operate a brake cylinder hone and a spray can, you can do a master cylinder. Make certain the old stuff matches the new stuff and that the piston returns as far with the new stuff installed as it did before.  Some kits seem to contain extra parts that if installed keep the piston from a full return, and they don't let the bleedback hole inside the bore get uncovered, so the brakes tend to build up pressure and drag.
 
If the bore cleans up nicely without pitting in the crucial areas where the seals would be during operation, you should have it made in the shade. Be certain to clean out all the holes and passageways with compressed air or whatever....(not that there are many to clean but there are all important.....)
 
If you want more info check out an older motors manual from the library and read up on brake parts rebuilding.  Newer manuals don't cover it much as it is more practical for a shop to simply install rebuilts.
 
When you reinstall, pay close attention to pedal freeplay and brake pushrod freeplay measurements. Making the pedal too "tight" will also allow the pedal to hold the master piston partially engaged and create drag in the brakes that only will go away if you bleed away the pressure ....and it will build right back up next time you use the brakes.
If you haven't checked out the tech FAQ section, go to:
http://www.thecj2apage.com/forums/tech-faq_forum57.html
for a lot of great stuff you need to know!!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote hillbilly21 Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2007 at 4:25pm
 Save time ..replace it with a new one for under 60.00....get the Jeep on the road summer is coming Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Turtleherder Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2007 at 7:32pm
Hillbilly. You and I both know the pleasure and reward of doing it ourselves and reaping the benefits later. Done right. It shouldn't take much longer than to just replace the old one with a NROS. Remember, there isn't an endless stream of parts. I say, let the rookie go for it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scott R Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2007 at 8:27pm
Originally posted by F Bill F Bill wrote:

Make certain the old stuff matches the new stuff and that the piston returns as far with the new stuff installed as it did before.  
 
If the bore cleans up nicely without pitting in the crucial areas where the seals would be during operation, you should have it made in the shade. 
 
You may have just provided the key phrases to my decision. It's not that this one doesn't work very well... it's completly shot and has been for a long time. Guess I need dig into it and see if there is any corrosion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote uglyjeep Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2007 at 10:33pm
Scott, if you find your core is unrebuildable, drop me an email, I have a used one here that I can check to see if its OK, and send to you for just the postage cost if you need it.  Let me know, thanks!
Daniel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dclear Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2007 at 8:44pm
I rebuilt mine, and the bore was rather "on the edge" but it does not leak.  Just be sure that all the pieces are in the kit you rebuilt with.  Last winter I went through all sorts of gyrations due to a missing part in the rebuild kit that I failed to notice, or, thinking stupidly, that it's absence was an "upgrade."
 
You don't get much wiggle room on these cast iron parts.  OTH you cant always depend on new parts--they sometimes are junk from the factory.  I'd trust Daniel--you can hone them out, and a hand drill operated hone is not all that expensive.
 
You win, you win.  You lose, You lose.  I think it's worth a try.  You can always start over with new, and there is really not much hassle in replacing a MC if you dont mind wrinkly paint.
 
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Scott R View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scott R Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2007 at 9:32pm
Daniel, Thank you very much! I just might take you up on that offer.
 
Once I get a couple hours of down time I'm going to look a little further into the one I have.


Edited by Scott R - 11 May 2007 at 9:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p3ferris Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2007 at 11:38pm
I rebuilt mine.  Never done one before and I found out it is very simple.  They make a rebuild kit and a hone for doing it.  Way less than 60.00.
Ed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scott R Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2007 at 9:54pm
Where is a good place to buy a rebuild kit?
 
I looked at Walck's and they list a Master Cylinder Repair Kit for $9.95
 
 
Seems awful cheap.... would this have all the goodies for a complete rebuild?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sean Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2007 at 10:09pm
Got mine at NAPA for $14.95.

The same rebuild kit works in many older vehicles, so it's fairly common.


Edited by sean - 11 May 2007 at 10:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p3ferris Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2007 at 11:18pm
Mine was 11.00 and some change
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaveyK01 Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2015 at 11:45pm
This is way after the original post, but my master cylinder is leaking and it has maybe 3K miles on it.  I replaced it during the rebuild of my Cj3A.  Question is could the parts be replaced without removing the cylinder from the jeep?  I can not see it needing "honed out" with so little use on it.  Are the repair parts a lot cheaper than a replacement cylinder?

Dave

Originally posted by Turtleherder Turtleherder wrote:

Hillbilly. You and I both know the pleasure and reward of doing it ourselves and reaping the benefits later. Done right. It shouldn't take much longer than to just replace the old one with a NROS. Remember, there isn't an endless stream of parts. I say, let the rookie go for it.
Dave
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