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Brake problems after 5 lug swap..

Discussion in 'Fox Body Mustangs' started by 331 LX, Nov 27, 2017.

  1. CW1343

    CW1343 Member Established Member

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    Any update now? Car looks great by the way. You may try looking into the booster if all else has failed. Good luck.

    Sent from my [device_name] using the svtperformance.com mobile app
     
    331 LX likes this.
  2. 331 LX

    331 LX Active Member Established Member

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    No updates.. I haven't had the car out since I did the pictures a couple of months ago haha.. Thank you for the kind words.

    I will get back on it this Wednesday because i'm going to change the oil for the first time in years. I've had a weird beginning of the year with my KTM, Ducati and Mustang having brake issues. LOL

    I think they just need to be bled on the bikes because all they did was sit in the garage during the winter, nothing else. I'm going to buy the proportioning valve to appease my father and if that fails we will do the booster. That leaves nothing else...
     
  3. crazycarlo

    crazycarlo Well-Known Member Established Member

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    I’m going to be doing a 5 lug swap/4 wheel cobra disc conversion soon as well.
     
  4. 331 LX

    331 LX Active Member Established Member

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    Nice - Definitely get the bigger cobra MC and proportioning valve for that setup. Good luck with it.

    Edit- Fixed the brakes on the bikes. They just had some air in the lines. I wish it was that easy on the Fox.
     
  5. crazycarlo

    crazycarlo Well-Known Member Established Member

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    Yes I already have the 93 cobra Mc, I’m getting the proportioning valve soon. Also going with stainless brake lines front and back.
     
  6. Mustang5L5

    Mustang5L5 Active Member Established Member

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    If you still have the rear drums on the car, you really shouldn't be installing a 4-wheel disk MC on the car, as the piston size is much too large for the amount of fluid required by wheel cylinders. There really isn't an ideal MC for use with some of the SN95 front disk setups when retaining rear drums, so the "best" MC to use is the stocker.

    The 99-04 GT PBR's caliper surface area is only 10% larger than the stock fox MC. Result will be a slightly softer pedal.

    The 1993 Cobra MC piston area is almost 2X the area of the stock fox MC so you area oversizing the MC by almost 40%. This increase in area is to account for rear disks, which require more fluid to move than smaller wheel cylinders. That's why there really isn't an ideal MC for a Sn95 front disk/rear drum setup. The stock MC actually gets you the closest unless you want to try and plumb in an 79-81 Fox MC with power brakes which has a 7/8" bore in it (~10% larger than stock). I wouldn't.

    Only thing I can say to try with your setup, OP, is to install the prop valve plug on the front of the combo valve, and install the adjustable unit. Bleed the brakes with it full open and see if that allows you to stock. Those front calipers are pretty powerful and you should be able to put yourself into the windshield (not literally) when you hit the pedal.
     
  7. John Grabowicz

    John Grabowicz New Member

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    Any updates on this?

    I made a mistake when I did my swap. I put 98" brakes on all four corners. A friend helped and when he bolted on the front calipers he put them on the wrong side of the car so the bleed valves were on the bottom trapping air in the top of the caliper. I couldn't figure it out for a few hours. We led and bled and bled them- until I noticed they were on the wrong side.

    I would just go through the car from top to bottom. Especially inspect line for small leaks under pressure.
     
  8. SVT-Cobra-1993

    SVT-Cobra-1993 New Member Established Member

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    I have done this swap a few times and just ran the factory master. Make sure your lines arent crossed, the front of the master should go to the back brakes and the back should go to the front brakes. Of course there is the extra fitting underneath that goes to the driver side wheel. You can take the stock proportioning valve apart pretty easily to make sure it isnt stuck. That might act like the fronts are leaking and send all the pressure to the rears since its more of a shuttle valve than a proportioning valve. There is a plunger with an o-ring and a spring, not that complicated. I just used a $20 Harbor Freight bleeder on my most recent project and it worked really well. Puts some suction on the bleeder and pulls the fluid through. Much easier than foot bleeding especially when starting from scratch and its great for changing fluid, just go until it comes out clear. Good luck getting it sorted and be sure to post up when you get it figured out.

    Mike
     
  9. May93

    May93 Member Established Member

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    I recently bought a 1989 Fox-body with the same upgrades. What was the outcome and solution to your problem?
     
  10. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    The proportion valve is needed.

    These do go bad and low to no pedal is happening.

    Reason is brake fluid is flowing back into master.

    To test We would clamp front brake hoses and pedal would be rock hard instantly.
    Being wheel cylinders only need a little fluid to push.

    You can use a hand pump
    To bleed the car solo.
     
  11. crazycarlo

    crazycarlo Well-Known Member Established Member

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    I finally got around to doing my brakes. I will say this. I replaced calipers, soft line and the rear hard lines. I also purchased the harbor freight pneumatic brake bleeder. To me complete junk. I don’t know if my compressor justxwasnt up to it or what. I bit the bullet and bought a Motive Power bleeder off Amazon. One of the best tools to buy to do brakes in my opinion. Had them done in like 20 minutes by myself.
     
    Bdubbs and May93 like this.
  12. Bdubbs

    Bdubbs u even lift bro? Established Member

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    The motive brake bleeder is awesome. I did my cobra brakes using it. I need to do the notch at some point. It has 03-04 cobra brakes.

    Sent from my Moto E (4) Plus using the svtperformance.com mobile app
     

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