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Front Disc Brake Tutorial

Discussion in 'Early CJ-5 and CJ-6 Tech' started by Focker, Oct 9, 2015.

  1. Aug 9, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    I have just completed my disk conversion and I cannot for the life of me get a consistent pedal feel. Right after the conversion the top part of the pedal travel was very soft and the new front disks were not really doing much of anything. I thought this was probably air in the system so I bled and bled and since I installed a remote reservoir at the same time I was able to use a power bleeder on 10 pounds of pressure, though I still didn't get any air out of the front calipers (my bleeders are on the top of the calipers so they are on the right way). So I decided to try it out again anyway and the same thing but this time as I was going down the road I would randomly push on the pedal and sometimes it would be nice and firm all the way at the top and it would stop fine. Then right after I let off the pedal and pushed it again it went back to being very soft. I cannot figure it out if anyone can help that would be great!
     
  2. Aug 9, 2016
    45es

    45es Member

    Naches, WA
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    You need to provide a more complete description of your brake system for anyone to be able to help analyze the problem. MC type? location? Drum/disc or disc/disc? Residual pressure valves? etc.
     
  3. Aug 9, 2016
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
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    From the 1st post... See if this helps.

    I think the biggest factor in the new brakes feeling great and worth the swap was "wearing" in the new pads. I bought the cheapest pads and maybe that was a contributing factor to the initial poor performance? Drive the Jeep a mile or two with your foot on the brakes a little (thanks jpflat2a). I completely forgot about this and was disappointed at first. The more I drive the Jeep the better the brakes function. Take your time bleeding the brake system and adjusting the rear drums. I also upgraded the rear drums to 11" at the same time and that made it hard to tell if the disc conversion was worth it.
     
  4. Aug 10, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    Sorry about that 45es. I have a stock dual reservoir mc located in the stock position under the floor. It is disks in front and drums in the rear. I have a wilwood 2 ib residual pressure valve right after the mc for the front lines. Could that pressure valve be bad so most of the time if it's not holding pressure in the lines a full stroke of the mc won't provide enough volume to the calipers to bite hard enough? Just a thought.

    Focker, I know this is not the problem because when my pedal gets firm every once in a while the front brakes grab nicely. I just don't have that consistent firmness in the pedal.
     
  5. Aug 10, 2016
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
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    Did you remove the stock check valve from the MC?
     
  6. Aug 10, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    I took the brass seat out and there wasn't a check valve behind it. I've heard that's common with aftermarket replacements.
     
  7. Aug 11, 2016
    45es

    45es Member

    Naches, WA
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    I have to ask. You describe bleeding the front brakes but, did you bleed the rear brakes also. If you pump the brakes, do they pump up and become firm?
     
  8. Aug 12, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    Yes i bled all of the brakes. No matter how much i pump the brakes they never become firm which is why i don't really think it's air in the lines.
     
  9. Aug 12, 2016
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
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    The 2lb RPV is installed with the flow in the right direction... Correct?

    Did you "wear" (break in) the new pads for a mile or so?

    Have you adjusted the drums?

    Do you have a rear 10lb RPV installed?

    Did you bench bleed the new MC?
     
  10. Aug 15, 2016
    jzeber

    jzeber Sponsor Sponsor

    San Jose, Ca
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    I had the same problem with my 71' for a long time. Do you have the brake lines routed correctly? I had to make sure the front brakes went to the first port (closets to plunger) and the back brakes went to the second port.
     
  11. Aug 16, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    Actually I just hooked the lines how the po had them which is switched from what you said. Did that fix it for you?
     
  12. Aug 16, 2016
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
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    *Edit - The port closest to the push rod needs to go to the front brake lines.

    As jzeber points out...You need to have the RVP valve going to the front discs as pictured in my post from page 1.
    [​IMG]
     
  13. Aug 16, 2016
    jzeber

    jzeber Sponsor Sponsor

    San Jose, Ca
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    Made all the difference in the world!
     
  14. Aug 16, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    Focker I have the rpv in the line for the front brakes, I just have that whole line going to the second port on the mc. I will switch the lines and see what happens. Thanks jzeber
     
  15. Aug 16, 2016
    jzeber

    jzeber Sponsor Sponsor

    San Jose, Ca
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    From a while back when I first did this conversion, post #42 on page 3. unfortunately the link is no longer valid but there was a ton of good info on it.

    D27 Disc brake swap on my 71'
     
  16. Aug 17, 2016
    CincyCJ5

    CincyCJ5 New Member

    Cincinnati, OH
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    Well, I switched my lines going to the mc last night and it seems like that did the trick. My jeep actually stops now! Thanks everyone for the help and thanks for that thread jzeber lots of good info in there.
     
    Daryl likes this.
  17. Aug 17, 2016
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
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    I labeled the line ports on the MC photo. Hopefully that will save others this troubleshooting time just in case theirs are switched too.
     
  18. Apr 15, 2017
    iharding

    iharding Member

    Tacoma, WA
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    Last edited: Apr 16, 2017

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