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1971 Master cylinder replacement

Discussion in 'Early CJ5 and CJ6 Tech' started by homersdog, Oct 16, 2015.

  1. Oct 16, 2015
    homersdog

    homersdog Tulsa, Ok 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Tulsa, OK
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    This isn't a build thread or anything, just a lesson learned on replacement master cylinders for the dual circuit MC in '71's and I suppose the other Dauntless years.

    My MC started getting soft last week, I checked the front calipers and the rear wheel cylinders, bled the whole system, no change. So I looked around at the FLAPS, Advance auto parts, O'Reillys, etc. They all listed part no. 10-1292 as the standard replacement. I could see in there stock photos they were selling the same rebuild MC under there own house brand names, but they all used the same stock photo.

    It was obvious from the pics the cylinder was different from the original Wagner which I still had installed. But I Figured for $26 I could get one and everything would work fine.

    But, as you can see by the photo below there are quite a few differences that would require a new plunger/push rod at additional cost because the new one had a deep pocket for the push rod to go in. Also it will need new brake lines because the fittings were different size. Then I would have a non-stock rigged up master cylinder, probably spending $50 more than the cylinder on the required parts.

    So my solution was: I bought an exact reproduction replacement MC for the Wagner from Crown for $111, free shipping. I bought through an ebay store, east coast jeeps. The extra cash will be worth it. I won't have to buy a bunch of extra parts to make it fit and it should be (hopefully) as solid as the original set up. I realize it is probably a Chinese repop unit, but the rebuilds from the Flaps were made in China too.

    http://www.crownautomotive.net/product/J0945556.html

    Old MC is on the left. I brightened up the top photo to show the .470 dia X 1.00 deep cavity in the new MC that prevents it from working with the old push rod.
    [​IMG]

    [​IMG]
     
    Last edited: Oct 16, 2015
  2. Oct 16, 2015
    BJHitson60

    BJHitson60 Member

    San Rafael, CA
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    I had the same issue with my 1970 recently. As recommended by some on this site, I sent mine to White Post Restorations in Virginia and they installed brass sleeves and completely rebuilt it. It is more expensive than the Crown but so far it has worked perfectly. Would be interested to know how the Crown unit works out.
     
  3. Oct 17, 2015
    homersdog

    homersdog Tulsa, Ok 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    I'll update this thread when I get it installed. Probably about 2 weeks.
     
    Last edited: Oct 17, 2015
  4. Oct 17, 2015
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Virginia Beach, VA
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    yep they are the place for vintage/classic car restorations
    White Post Restorations in Virginia
     
  5. Oct 17, 2015
    Dawgy

    Dawgy Member

    Decatur,Alabama
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  6. Oct 17, 2015
    BJHitson60

    BJHitson60 Member

    San Rafael, CA
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  7. Oct 17, 2015
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
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    I just got one from him too a couple months ago. It is just like the original. Mine works good. I did the same thing. Bought one of the replacement ones and ran into pushrod issues. Mine finally jambed up and had to get the new crown one that works.

    Worth the money to stop;)
     
  8. Oct 17, 2015
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Fwiw: I put the crown mc in 2.5 years ago all has been good since.
     
  9. Oct 22, 2015
    homersdog

    homersdog Tulsa, Ok 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    The new MC arrived today from crown. The casting has a few minor differences, but overall looks good. Maybe this weekend I'll squeeze some time it to change it, but Probable next weekend.

    [​IMG]
     
  10. Oct 23, 2015
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    Can you see RPV'S in the outlets?
     
  11. Oct 24, 2015
    djbutler

    djbutler Sponsor

    Rio Linda CA
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    Have you opened up the new Crown unit to see if it has a stepped bore like the original Wagner Lockheed?

    Don
     
  12. Nov 1, 2015
    homersdog

    homersdog Tulsa, Ok 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Focker: Yes, it has the Residual pressure valve, I removed the front one as you can see here. It is similar to the Wagner RPV, but not exactly the same.

    Don: no I did not open the main part of the MC, I did not want to screw something up before I used it.

    I got the new MC installed Friday evening and took it around a few miles, seems to be working fine. Very solid. One thing I did not like: the manufacturer did not do a good job of tightening all the fittings. The drain plug was just little more than finger tight, the port adapters need a little snugging down too.

    [​IMG]
     
  13. Jun 29, 2019
    djbutler

    djbutler Sponsor

    Rio Linda CA
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    Focker, (and anybody else interested in this) I have opened up one of these Crown MC and looked at the bore size. It has a straight 1" bore for both pistons, not the stepped bore size of the original Wagner MC. This ought to work fine depending on the size of the wheel cylinders. The original stepped bore would put higher fluid pressure on the front brake wheel cylinders to prevent rear wheel lockup.
    Many of us have upgraded to 11" brakes all the way around, with a smaller bore wheel cylinder in the rear brakes. The Crown unit should work fine in that application. I haven't tried yet to see if it will push enough fluid for a front disc application.
    Don
     
    Focker likes this.
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