Brakes Front brakes heating up, pressurizing fluid, pedal stays up

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Mustang5L5

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Actuslly, if you convert to rear disks, it would be strictly a bolt on thing. Adapter kits and lines are readily available.

fix the brake issue now, do the rear disk and modern MC swap at the same time. Will make MC life easier because there is a bolt in brake line adapter kit. One less MC to bench bleed and deal with.

technically you could use it now with an 87-93 MC if you plug the bottom port. Seems a little...hack though. But it could work. But then it all goes in the trash when you do rear disks becUse that’s a different MC
 
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MRaburn

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OK, problem still exists.

  • installed new caliper
  • reinstalled tested brake line
  • bled brakes
  • while bleeding brakes, the caliper would seize the rotor on the pumps and let go on release, I could spin it freely.
  • cranked car, let booster activate and press the brakes in.
  • now it's locked up again ONLY on passenger side... again.
  • Im stumped.
Mike
 

7991LXnSHO

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Was the tested line the hose, or did you also check out the hardlines?
Edit, you have to be looking for a cliff to push it off of.
 
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MRaburn

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Yes. I had no brakes at all with old master cyclinder. I replaced it and this is when the lock up started.

That’s why I thought old calipers were bad. So replaced them and same issue.

But why just one side. I have no issues replacing it if that could. E it. It’s rusted up and need a clean one in the engine bay.
 

Mustang5L5

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This is strange. Cracking that bleeder should allow the piston to retract. Might take a few spins of the wheel to do it
 

MRaburn

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OK, I release pressure on the bleeder valve and I was able to start spinning the rotor and the more I span it the free'er it got as in normal.

So what's holding the pressure. I have an 89 proportion valve lying around, should I look for an aftermarket one to replace it that will have the right fitting ends?
 

Mustang5L5

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I'm starting to think there's a blockage in your proportioning valve.

Which caliper is it again that is freezing up? The two front lines are split. One should go to the rear, and one comes off the bottom, rear port of the PV. I'm thinking one of these ports might be clogged. When you step on the brake pedal, you have more than enough power to force fluid past a blockage, but the natural wobble of the rotor might not be enough for it to flow back.

The problem is the fitting layout of the PV is different on the 87+ cars as they are a 3-port MC with one line direct, and a 2 port PV with 2 lines in and 2 out. The 80-86 PV is 2 in and 3 out. I also am not sure if the fitting sizes are the same. I believe the 87+ is a mis of 3/8-24 and 7/16-24 inverted flare.

The part number for the 80-86 PV is E0ZC-2B328-AA, You can either try to replace it, or remove it and rebuild it like the link I posted several posts up.

If you've replaced the MC, the calipers several times and tested the lines, it's the only think that it could be.

One more question. When you bleed the front brakes, do they both bleed at the same flow, or is the sticking wheel a little slower to bleed through?
 

MRaburn

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The right side is the one sticking. It did seem to bleed slowly. I have not blown out the metal line from the pvalve to the caliper.

So you think I need to remove the proportion valve and try to clean and rebuild?

When I was bleeding the brakes with no booster assist, the caliper would relax back, it was just after enough pressure was applied with the booster that the right side stuck.

Mike