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Cj2A master brake cylinder

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Thing 2 View Drop Down
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    Posted: 10 June 2018 at 11:51pm
my 46 CJ2A needs a new master cylinder. If I give you the VIN number ( 63563 ) can you tell me which one to order. Two choices are: #1 front mounting hole is threaded. Or #2 both front mounting holes are not threaded, goes straight through. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2018 at 12:24am
According to Walck's its this one:

But why don't you just look and see what is on it now? That would eliminate any guess work. No telling what has been changed over the  last 72 years.
1948 CJ2A - It goes nowhere fast, but anywhere slow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thing 2 Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 1:39am
I found out that you can determine which kind of master cylinder you have by measuring the bolt distance c/c. If it’s 3.25” your master is the “ front mounting hole is threaded “ variant. The other variety is straight through and wider c/c than 3.25”. Now, I still have to drive 155 miles to inspect the thing. 
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Ol' Unreliable View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 2:15am
That's some useful info.  Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 4:29am
Do they break it down into "early" vs "late"? If so, I'm sure you need the early one, I don't think that was changed until the frame was changed in '49. Or you can check and see what the CJ3A/B call for. I'd bet that they use the same as the "late" CJ2-A. You would need the other one.   BW

Edit: I just checked the parts manual. The "early" master cylinder is part # A-556, and is used thru serial number 215649. Part # 647558 is used on "late" CJ2-A's after serial number 215649, and all CJ3A's. An aluminum master is mentioned for the later models, which I've never seen. 
  If you would like, I can measure the bolt center distance on one of my '47s tomorrow.    BW
It is NOT a Jeep Willys! It is a Willys jeep.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote WeeWilly Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 2:07pm
The master cyl. bodies are also different in shape between the early and late. The early has a round tube like shape to the reservoir  while the late has  more of a square shape to it.

   Jim
47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj2a Quote  Post ReplyReply Direct Link To This Post Posted: 15 June 2018 at 1:14am
Yes, I just replaced my MC, very easy to tell the difference. Just take a look  at the frame and you can usually tell immediately.  One version bolts through the frame, the other bolts into it.

otherwiseee measure from bolt to bolt.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SnorriS Quote  Post ReplyReply Direct Link To This Post Posted: 21 June 2018 at 8:53pm
How much pitting in a master cylinder is salvageable with hone?
48 in process
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 21 June 2018 at 9:16pm
Not much. A good rule of thumb is if you can feel the pit with a fingernail, it's too deep. New master cylinders are pretty cheap. For all the effort of trying to hone it and then it may or may not work, I'd just get a new one.
1948 CJ2A - It goes nowhere fast, but anywhere slow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SnorriS Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2018 at 2:03am
tThat was my thought as well.

Thanks for the opinion.
48 in process
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2018 at 3:28am
How much does it cost to have a master cylinder sleeved?

BTW, welcome to the page, SnorriS!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2018 at 3:46am
Originally posted by Ol' Unreliable Ol' Unreliable wrote:

How much does it cost to have a master cylinder sleeved?

BTW, welcome to the page, SnorriS!


The last time I looked into this, the sleeve repair cost almost three times what a new master cylinder cost. Of course, YMMV.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2018 at 4:00am
I guess sleeving is for the restoration purist.  The ones with m-o-n-e-y.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wadoyado Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2018 at 4:20am
Don't mean to hi-jack your thread Thing 2 but you might find this of interest. I bought this (advertised as NOS Cj2a MC repair kit). The piston measured 1 1/16" dia. Thinking I needed to ream the MC to size, I brought it to my cuz's die shop. In the process this steel sleeve came out like it was meant to be removed for the oversized repair kit. The surface was shiny smooth so I installed the oversized kit and kept my fingers crossed. Brakes work(1mi on the road) and don't appear to leak. Anyone else ever encounter this? Joe W
"It's unbelievable how much you don't know about the jeep you've been driving all your life" (Mickey Mantle paraphrase)
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SnorriS View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SnorriS Quote  Post ReplyReply Direct Link To This Post Posted: 26 June 2018 at 12:42am
Thanks for the welcome.
As a follow up, I bought a little brake cylinder hone. Small amount of old caked on material came out easily and left the MC in good shape. 

A little history on my '48. It was well cared for by the previous owner. He passed away in the mid '80's and it has sat since then. Brake fluid dries out. Gas dried out. New oil in engine and oil bath air cleaner and she turns over by hand easily. So just some system cleaning and brake cylinders cleaned out and rebuilt and I expect it will be rolling to new adventures soon.

Hope to make some friends here as I have questions or post some sucsessful til I learn along the way.

-S
48 in process
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