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Old 07-29-2015, 07:19 AM
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Poor braking

On my 28 roaster, I was having problems with a leaky master cylinder. I replaced it using a '73 pinto master cylinder (duel reservoir). Although not exactly like the one I replaced, it was very similar and as close as I could find to the one I was replacing (the pushrod was the same style and length). I have disc in the front and drums in the back. Oddly, there is no external adjuster port for the back brake shoes. I have to "stand" on the brake pedal to stop and I can't lock the brakes up.

When I replaced the master cylinder, I reverse bled the lines and then power bled them. I am 99.9% confident I do not have air in the lines and I do not have any leaks. Their seemed to be plenty of pad left on the rear shoes and front pads. Any ideas on what I may be overlooking? Could it be a problem with the bore size on the master cylinder? The lines off of the master cylinder go into a proportioning valve (two lines in four out). I don't know what else to check.

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Old 07-29-2015, 07:24 AM
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Some factory style proporting/metering/safety valves have to be manually reset
dave
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Old 07-29-2015, 07:31 AM
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Hmm...I am not familiar with that process. Can you describe the process for me? As I think about it, the master cylinder I removed, the fitting on the small chamber was larger than the other fitting (on the large chamber). On the new master cylinder, it is just the opposite. I did not think that would make a difference except I had to make new lines. Thoughts?

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Old 07-29-2015, 08:50 AM
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If this is your problem , & you're sure you have the system bled , usually a sharp STOMP of the pedal will reset the valve , do a little googling , lot's of info . Ford had some bastard fittings on there MC's ... to the best of my knowledge pimto , bobcat, granada , monarch , mustang , etc. all used a common MC in that ers..
dave
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Old 07-29-2015, 02:06 PM
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Thanks...I did as you suggested and just stomped on the brakes. The brakes did lock up, but when I apply pressure slowly, I can't get them to lock up. It just does not feel right. I don't feel that progression in slowing down. I guess I don't feel like I have control of the pressure.
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Old 07-29-2015, 02:14 PM
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Since you're working on it , pull a rear drum & check to see if it's adjusted properly....in order for self adjusters to work you have to come to full stop in reverse...
dave
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Old 07-29-2015, 02:23 PM
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Ha...I had not thought about these being self adjusting. I will give that a try.
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Old 07-30-2015, 05:44 AM
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brakes

what was bore size on old mc compared to new mc
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Old 07-30-2015, 06:54 AM
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Unfortunately I do not know. I and several others could not determine the origin of the old MC. I suppose I could take it apart and try to determine the bore size.
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Old 08-01-2015, 12:38 PM
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Check your vacuum goin to the booster..

I had the same issue.
after rebuilding my motor i went down to 10 inches which will work but not well.

You need to have at least 17-22 inches of vacuum for power brakes

Also verify that the master cyl you are currently using is designed for rear drum and front disc and not for 4 wheel disc.

If I understood correctly, disc breaks require more fluid volume and drums require more pressure

But i would definitely start by checking the vacuum

Hope this helped
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Old 08-01-2015, 03:03 PM
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MP Brakes has some good guides to braking and will usually guide u thru on the phone. They used to have a small book available that had diagrams that were beneficial. http://www.mpbrakes.com/troubleshooting-guide
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Old 08-08-2015, 05:50 PM
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Where is the MC located? could it be the need for a residual valve?
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