66 w/4wheel disc brks. low pedal - Ford Mustang Forum
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post #1 of 11 (permalink) Old 4 Weeks Ago Thread Starter
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66 w/4wheel disc brks. low pedal

have 66 coupe with 80 Granada frt. disc brks. has late 90,s explorer rear end w/explorer rear disc brks.only proportioning valve is adjustable one plumbed into rear brk. line. master cyl. is 95 mustang gt 4 whl. disc pwr. brk. w/ 1.06 bore diam.parts books show Granada disc/drum setup using master cyl. w/.094 bore diam. show explorer using master cyl. w/ 1.06 bore diam.so I believe master cyl. is sufficient for this setup. have bled system repeatedly. have taken calipers loose & pressure bled w/bleeders all at top,no air present,only solid fluid.started pinching off hoses,l.frt. no noticible difference. rt.frt. noticible difference in pedal.replaced rt. frt. caliper w/ reman & pressure bled w/ bleeder atopno improvement. pinch off hose to rt. frt. caliper again,better pedal. pinch off hoses at rear calipers & rt. frt. caliper,have good solid pedal.if I pinch off hoses to all 4 calipers I have awesome rock hard pedal approx. 3 in. from carpet with my full weight on brk. pedal.this all points to a problem in the calipers but since repacing the rt.frt. caliper did not help,i am hesitant to start throwing parts at it. there are no leaks anywhere & no visible signs of any problems w/any of the calipers & no air present when bleeding. the rear calipers & l.frt. caliper came on the car,not sure of their age or if used or reman. any ideas or help would be greatly appreciated as I am losing any patience I ever had with this. thanks in advance. jim

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post #2 of 11 (permalink) Old 4 Weeks Ago
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Jim, just to go over some basics that might help you narrow this down, start with what it's doing. "Spongy" brake means that something's compressing or expanding. That means you either still have some stubborn air in there, or else something in the system is giving. How are you pinching off the hoses? Do you mean the soft lines? If those are not in real good shape, it's possible that they are expanding like balloons and giving you some of the problem. Given your sleuthing, it sounds like maybe there's still just air inside the brake pistons. Did you install them with the bleeder upside down maybe? If it's not pointing 'up' then no amount of bleeding will ever get the air out of the chamber, because it's trapped above like a bubble.


Like you said, just a few ideas! Frustrating as this is, I bet we can figure out what's going on so you don't end up throwing more money at the problem.


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post #3 of 11 (permalink) Old 4 Weeks Ago
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Grimbrand I think he means that there is a lot of travel until 3" from the floor, then the pedal is "rock hard". That would not be "spongy", or point to soft hoses or air in the line.

Sounds to me that a mechanical adjustment to the brake pedal rod is required.

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post #4 of 11 (permalink) Old 4 Weeks Ago
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IMHO, I would 1st look at the master brake cylinder...ÖÖ.

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post #5 of 11 (permalink) Old 4 Weeks Ago
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You might want to review this video:




Adjustment of master cylinder push rod.

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post #6 of 11 (permalink) Old 4 Weeks Ago
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I hope you get this figured out. Sadly, it's another case of "just because it fits doesn't mean it will work". Good luck.
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post #7 of 11 (permalink) Old 4 Weeks Ago
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Have you bled the brakes like this? right rear, left rear, right front, left front. If not, try this first.
Otherwise it could be the wrong length push rod.
Next time, stick to all things Mustang.

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post #8 of 11 (permalink) Old 4 Weeks Ago Thread Starter
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just a quick update.master cyl. is new,not reman.booster to m/c pushrod already ckd.has 1/32 inch clearance before activating m/c.proportioning valve is turned clockwise in fully for max. pressure to rear calipers.all calipers mounted correctly w/bleeders at top.have ckd. piston to brk.pad clearance to make sure piston stays in contact w/brk.pads when brks. are released.have bled too many times to remember both w/someone pushing pedal while bleeding & w/pressure bleeder,never get any air,only solid stream of fluid.car stops okay but pedal goes to 1/2 in. from carpet before travel stops. if I start pinching off brk. hoses at each wheel,will get solid pedal 3 in. from carpet by time all are pinched off.have bled rr/lr/rtfrt./lfrt. in that order.thinking of borrowing gauge set to ck. pressure at each wheel next & see what I have.
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post #9 of 11 (permalink) Old 4 Weeks Ago
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How are you 'pinching off hoses'?

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post #10 of 11 (permalink) Old 4 Weeks Ago
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If you pinch off a brake hose you ruined it.
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post #11 of 11 (permalink) Old 4 Weeks Ago
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Perhaps this would help:

https://www.cjponyparts.com/scott-dr...SABEgJQGvD_BwE

This part "moves" the MC attachment point further down the brake pedal arm, which increases the travel of the push rod.

Hope this helps.

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