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  1. #51

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    Basically the pushrod that goes through the booster...my M1858 (part number) Master Cylinder came with one too. Do I have to swap those out? I'll try and get a picture here soon.

    Looking at the booster though, this doesn't look like an assembly I want to tear into if I don't have to.

  2. #52

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    Here's what I'm trying to explain. My thinking is the stock rod will still center in the new (larger bore) master cylinder and get the job done despite not being thicker in diameter like the supplied unit...but this is also the first time I've ever dealt with a master cylinder swap so, I don't know what I'm not thinking of.

  3. #53

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    The pushrod is generally referred to as a dogleg or a straight pushrod, depending on whether it has a bend in it or not.

    This has absolutely nothing to do with the m/c. It has to do with the booster, brake pedal, pedal box and year of the chassis. Those are the parts that need to match the pushrod. All 1979-2004 Mustangs need to use the dogleg pushrod with the exception of the 1996-98 V6 Mustang.

    I don't have any data on Fairmont applications. You should install which ever pushrod type was originally installed in the car.
    Jack Hidley
    Maximum Motorsports Tech Support

  4. #54

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    First off...1) I learned something new today, so thanks

    2) Essentially you answered my question. i'll keep the stock dogleg pushrod in the stock booster and reinstall that. So there's not going to be a problem that the girth/thickness/diameter of the straight push rod that came with the M/C is larger than the one that's in the stock booster?

    Thanks for your help!

  5. #55

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    2) Nope.
    Jack Hidley
    Maximum Motorsports Tech Support

  6. #56

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    Thanks again! Now I wished I didn't take the booster out! It was a pain parked in my garage where the drivers door can't swing all the way open, but this isn't the worst thing in the world either. I'll survive. Thankfully I'm double jointed, fairly flexible and not claustrophobic. Will have to contort myself again with many different lengths of socket extensions, but I'll survive.

  7. #57

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    Jack, I'm in need of more help. I'm fighting something and have no clue what it is I'm fighting. More or less I went through more trouble shooting this weekend, only to end up back where I was 2 weeks ago (see video link) -

    https://youtu.be/tJmx5goQxr0

    You can skip to like 6:10 in the video.

    So where I'm left now is wondering (among many things) if there's something I'm trading off with my dual port style Master Cylinder ( M1858 ) with 1" bore, whereas it appears (or I assume) the 1993 Cobra 1" bore Master Cylinder is a single reservoir?

  8. #58

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    Whether the m/c has dual or common reservoir won't make any difference as far as the brakes working or not.

    Since you installed a new m/c, you need to bench bleed the m/c. I would do this on the car, with it in place. Put rags under the outlet nuts on the m/c. Crack each nut open about 1/4 turn and use it as a bleeder screw the same as if it were a bleeder nipple. The brake fluid and air will come out the threads. Once you have bleed both outlet nuts, then bleed the rear brakes, then the front brakes, then the rear brakes again. This should get all of the air out of the system.

    If this doesn't work, I would take apart the stock proportioning valve, clean all of the parts, lube it with brake fluid and reassemble. Then bleed the brakes again.
    Jack Hidley
    Maximum Motorsports Tech Support

  9. #59
    FEP Super Member erratic50's Avatar
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    If you are using SVO/lincoln style rear brakes with fairmont/mustang style front brakes you will not have rear brakes. You need an SN95 style rear brake to get the caliper diameter down to where it will try to stop

  10. #60

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    His car has Varga rear calipers, so they are not from an SVO (Kelsey Hayes).
    Jack Hidley
    Maximum Motorsports Tech Support

  11. #61

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    Thanks Jack. Yea I bench bled it a few weeks ago, then bled it in place yesterday and ended up with the same results as two weeks ago. I'll look into cleaning the stock proportioning valve (I do have it gutted and a manual adjustable in). Couldn't hurt. I'm kind of thinking maybe I just have a crap new Master Cylinder. When I was bench bleeding, it seemed like on one pump all of the sudden it was a little easier to push in. So I wonder if I destroyed some internal seal or something?

    And yes erratic, although it took awhile to figure it out, as Jack mentions I do have Varga style calipers 91-92 Mark VII specific, are also the same caliper (verified on auto parts store website) used in the rear of 93 Cobras. I think that's covered within this thread even, but it's been awhile ago now since I discovered that.

    Another hypothesis I have, is that there's a bad relationship between the pushrod length in a stock fox body booster compared to the throw required on the M1858 Master Cylinder (basically a 85 lincoln Town Car M/C). Thoughts on that?
    Last edited by Str8sixfan; 11-11-2019 at 08:40 PM.

  12. #62

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    The stock proportioning valve is not just a proportioning valve. The valve at the front of it is a proportioning valve. The valve at the rear of it is a differential pressure valve. If you "gutted" the valve, most likely you only removed the parts in the front of it.

    When you bench bleed the m/c, it should become more and more difficult to push the piston in it. If it gets easier, that means that there is air in it.

    The pushrod length has absolutely nothing to do with the brake pedal going to the floor. The pedal ratio is around 3.4:1, so if the pushrod was 0.1" too short, the brake pedal would have 0.34" of free play in it, before it started moving the piston in the m/c.
    Jack Hidley
    Maximum Motorsports Tech Support

  13. #63

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    OK awesome on all accounts, I now have follow up questions...

    So did I remove too little or the right amount of the stock prop valve? https://youtu.be/cu3bdm6kyIs

  14. #64

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    In the video, you removed the proportioning valve parts from the combination valve. This is correct for what you are doing.

    The differential pressure valve parts are located in the opposite end of the combination valve. On your car, you will probably need to remove the brake line coming out the rear of the valve housing to get these parts out so that you can clean the valve out.

    https://farm5.staticflickr.com/4893/...b9d07f46_z.jpg
    Jack Hidley
    Maximum Motorsports Tech Support

  15. #65

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    I'm sorry for being so picky here...but, to make sure I'm understanding you correctly...

    To date, I'm where I need to be on the stock proportioning valve. I would only need to disassemble the differential pressure valve parts on the rear end of it if I decide to clean it out. Then I would reinstall the differential pressure valve after cleaning is done.

    Is that correct?

  16. #66

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    Correct.
    Jack Hidley
    Maximum Motorsports Tech Support

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