1. diesel_lv

    diesel_lv Well-Known Member

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    1967 Coronet, did front disc conversion using Dr Diff. Kept manual brakes. Used air bleeder to draw a vacuum n bleed from passenger rear, driver rear, passenger front, driver front until no air and all nice clean clear brake fluid. Pushed pedal and it went to floor. Pumped it a couple times and firm as can be. Now been driving it, trying to work out engine, fi, etc.. bugs and brakes started getting mushy. Then almost to the floor. I bleed them again and the brake pedal did the same thing. To the floor, pump a few times and very firm. I found no sign of leak at rear cylinders, any connection point, distribution block, master cylinder. Anyone have any ideas on this? Thanks
     
  2. 493 Mike

    493 Mike FBBO Gold Member FBBO Gold Member

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    Did you use a new master cylinder? Bench bleed it?
    Mike
     
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    • vance.dykes

      vance.dykes Well-Known Member

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      it is sucking in air from the rear of the master . wont see any leak from that . if you have rear drums the wheel cylinders can do this also.
       
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      • hunt2elk

        hunt2elk FBBO Gold Member FBBO Gold Member

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        Sure sounds like you still have some air in the system.
         
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        • Billccm

          Billccm FBBO Gold Member FBBO Gold Member

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          Okay when you bleed after a spongy pedal do you see bubbles? If so, what particular line has the bubbles? I spent 6 weekends chasing what you describe and it was a bad flare. I had no fluid leaks whatsoever.
           
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          • slimt

            slimt Well-Known Member

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            I wonder if its the inside bore size of the cylinder causing that issue. I thought for a manual brake it was suppose to be a 7/8 bore size for pressure? I had to do that with my 55.
             
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            • diesel_lv

              diesel_lv Well-Known Member

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              Yes, new master cylinder from Dr Diff. N yes, bench bleed.
               
            • diesel_lv

              diesel_lv Well-Known Member

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              When I re did it yesterday, I saw bubbles in all the lines. But the fluid level was up. I bleed w the air bleeder until no bubbles at each wheel. Well that sounds like fun, checking every flare. Or as above, possibly air bleeding in from back of master cylinder. Is there a way to check/test? Since no fluid coming out
               
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              • vance.dykes

                vance.dykes Well-Known Member

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                WHEN I DO THIS I STAY ON SIDE ROADS ONLY!!!!!!
                i would take a brake hose clamp put on the rear brakes as to take out that part of the system then do what is needed to drive carefully only hafe of the brake system and see if the pedal drops. then i will move the clamp to the right front then the left. this will help isolate to find bubbles. checking all flares take your line wrench loosen and tighten 2 or 3 times a little tighter each time this may help seat the flares.
                 
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                • diesel_lv

                  diesel_lv Well-Known Member

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                  It took about 300 miles of short daily drives over a month to get spongy.
                   
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                  • Billccm

                    Billccm FBBO Gold Member FBBO Gold Member

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                    Bubbles in all lines is probably something else. I had bubbles at the left front only.
                     
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                    • 65wgn440

                      65wgn440 Well-Known Member

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                      If you are definitely not losing any fluid, then I would warranty/replace the master cylinder.
                       
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                      • vance.dykes

                        vance.dykes Well-Known Member

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                        then i would go over all flare line nuts and see what happens if it returns then i would replace master cylinders. and don't get a rebuild get new i have had so many bad out of the box or fail in a week .
                         
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                        • bm02tj

                          bm02tj Well-Known Member

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                          If any one puts a clamp on one of my brake hoses they have to replace as it can damage the inner liner
                          I would never use one unless I had no other option then replace hose asap
                           
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                          • khryslerkid

                            khryslerkid FBBO Gold Member FBBO Gold Member

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                            Hows your rear shoes adjustment? Too much travel can put the brake pedal close to the floor.

                            I've never found any of these bleeding devices to work like they should. Ever time I hear of someone having problems with air in the lines they say they are using one.

                            To do this by yourself...Use a glass bottle and a piece of long hose to fit on the nipple. Have some brake fluid in the bottom of the bottle so the end of the hose will be submerged and not suck any air. Brake the nipple loose and give the pedal two or three slow pumps. Then tighten the nipple. Check the level in the master cylinder after each wheel.

                            Right rear, left rear, right front, left front.

                            Are the bleeders on your front calipers at the top? Some installations will have the bleeders at the bottom and you'll have problems bleeding.
                             
                          • vance.dykes

                            vance.dykes Well-Known Member

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                            as a 40 year experience master a s e tech if you know the right tool and how to use them there will never be a problem.

                            people ask for help and all some of you want to do is tear people up for your lack of knowledge.
                             
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                            • bm02tj

                              bm02tj Well-Known Member

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                              The problem shows up a year or so later
                              So I still know it is wrong to pinch brake hoses
                               
                            • Frankb

                              Frankb Well-Known Member

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                              Make sure the bleeders on the new calipers are pointed up. As straight up as possible.
                               
                            • vance.dykes

                              vance.dykes Well-Known Member

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                              1. this in a test in repair manuals and snap on and other tool maker sell the brake line clamp if you did this for a living you might understand.
                              2. your complaint of it will take a year tells me that it is air sucking in to the system.
                              it will be hard to tell exactly what with out isolating one component from the system to know exactly the part failure.
                               
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