1. ScamperTom

    ScamperTom Well-Known Member

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    Hi all, this is a pretty basic question, I think. My Scamp recently started braking really badly (fading, pulling hard to the right). I found that the front wheel cylinders were both bad. One leaking, the other stuck. I replaced the cylinders, drums, wheel brake lines, and bled them. They now work fine with light braking, but after extended use or even one hard brake, I now experience massive brake fade. The pedal goes all the way to the floor and I can even sometimes completely depress it even if the car seems to be otherwise braking fine.

    Looking in the master cylinder, the brake fluid appears very dark brown, even after putting in at least a pint of fresh fluid, with what appears to be a sort of sediment. It looks like the inside of the master cylinder is rusty, and contaminating the brake fluid. I suppose this might be what caused the wheel cylinders to go bad in the first place. I know that brake fluid is hydroscopic, but would this cause the brake fading issues?

    To fix this problem, can I just flush the fluid, or do I need to remove the master cylinder and clean out the rust first? Can I attempt to clean it without removing it from the car? I'm just afraid that if I remove it I might cause more issues.

    First time working on brakes here... Thanks for the help!
     
  2. Murray

    Murray FABO Gold Member FABO Gold Member

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    You need a new M/C.
     
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    • Tooljunkie

      Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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      I would have to agree. Rust is abrasive, and it is likely to the point where master cylinder is worn out.
      May want to look at the other two corners as well. A good flush through the lines will be necessary.
       
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      • ScamperTom

        ScamperTom Well-Known Member

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        Thanks for the input y'all. For some reason I didn't even think that a worn out master cylinder could be it... obvious. Looks like I'll be pulling it.
         
      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        Brake fade and pedal to the metal (going down to floor) are two completely different things.

        Brake fade is overheating the lining and drums until they won't stop. If you had a problem that caused brakes to drag (like a stuck cylinder) they can glaze and cause fading, or even poor braking cold

        Pedal going to the floor or leaking down is either shoes out of adjustment, air in the lines, or master cylinder seals leaking internally, "past each other." The classic leaking master is you push fairly "sharp" and it will brake, but if you gently "let off" pressure and apply light pressure, it will slowly sink to the floor.

        Rusty fluid? Might be able to flush on a newer car, but on girls this old you may have OTHER problems like rusting lines, rusting cylinders etc. Time to tear the thing apart and see what is there

        After all, it is your life and the lives of others, here......................
         
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        • Divenut

          Divenut Well-Known Member

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          Another vote for new MC (And probably new lines etc).... I experienced poor braking, pulling, fade and overall scary lack of stopping power. Decided to go with front disc conversion so a new MC was in order anyway. When I started pulling the old stuff apart, it became very apparent that the entire system was in poor shape. Replacing all the lines (original ones were brittle at heck, and the rubber section were dried and cracking), new proportioning valve and fully rebuilding rear drum brakes with new components.

          Here's my MC...

          Pat

          20190216_100703_resized.jpg
           
        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

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          You can also take a look at the cylinder condition (internal). If its not scratched up, rebuild kit will put you back in business after a good cleaning. Time vs. money and a roll of the dice no matter what you do.
           
        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          I haven't checked lately, but a rebuilt cylinder used to be within a few dollars of a kit, and the rebuild is guaranteed. I would not kit it........and you need a hone as well........unless there is no other choice.
           
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          • Mattax

            Mattax Just the facts, ma'am FABO Gold Member

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            With the quality of rebuilt stuff, everything seems like a crapshoot these days. That's why I mentioned the option if the bore is clean. Also, at least for me, it depends on how difficult it is to get a correct master cylinder. There's so much mix and match with the big rebuilders these days... You know that story
             
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            • ScamperTom

              ScamperTom Well-Known Member

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              Thanks for clarifying. I used the term because the brakes only stop working after use, but i see that’s incorrect. This is my dd, so it really needs to stop!

              Yup that’s what mine looks like.

              I guess I just assumed i could rebuild it. I didn’t think about the rust possibly damaging the cylinder. Will a couple scratches really cut down on braking power that much?
               
            • Mattax

              Mattax Just the facts, ma'am FABO Gold Member

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              If you see scratches in the bore, that are deep enough to catch a fingernail, or won't clean up with emery, it won't seal. It will have to be honed,
               
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              • 67Dart273

                67Dart273 FABO Gold Member FABO Gold Member

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                You need to hone it generally no matter what. Especially something this old. O'Reillys auto parts loans some tools, don't know about brake hones
                 
              • ScamperTom

                ScamperTom Well-Known Member

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                Well I guess I'll have to bite the bullet. I'll check the bore, but it sounds like the surest way to go is probably just get a new mc. Thanks for y'all's help!
                 
              • MoparLeo

                MoparLeo NRA PATRON LEVEL LIFE MEMBER

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                I would use caution being that you said you are new to brakes. Do not do this alone. Get the help of someone who Is familiar with doing brakes, not just putting shoes on. Really, brakes are the most important mechanical system on a car. Number one. When they get this old and you have rust in the system, it will be in the whole system. Personally, whenever I have purchased an older car the first thing that I have done is a complete brake system overhaul. Not really expensive especially when you consider the possible alternatives. Get a good book on brake hydraulic systems and read it several times. Get familiar with the terms and what everything does. Always have an assistant with experience. A clean work area. Plenty of space. Proper tools. All of the proper parts. New, sealed brake fluid. Plenty of light, clean rags, brake clean spray. Don't try to rebuild brake parts when this old unless they are just not available anymore. Buy new and buy Western mfg. parts. Not Eastern/Asian parts if possible. New bearings, races, seals, brake hardware kits (springs, clips etc...) premium shoes, wheel cylinders, hoses, possibly metal lines if rusted, drums if oversized, New not rebuilt Master Cylinder. If you can't afford all of the stuff at once, don't buy cheap stuff instead just so you can get it done. Again this is the most important system on your car. Safety first. Just make your self a list and buy what you can afford, a part at a time if you have to until you have everything that you need and get the best quality that you can get. Remember that everyones life may depend on it and you won't have to replace these parts again for many years if maintained properly.
                 
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                • Tooljunkie

                  Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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                  This is all excellent advice. I commend all of you.
                  I didnt feel it was my place to mention the fact that op was new to brake work and should seek help when repairing them. But mopar leo is dead on the money.

                  Being in the trade i can say that your brake system is one of the easiest to service,and with the assistance of someone knowledgeable it will all become obvious as you work on it.

                  New master cylinder all the way.
                  But pull the old one apart and look at it, if anything just to understand and satisfy your curiosity.
                  I had a brake service manual from the 40’s,it was thorough in the service and overhaul of all the brake components. I may check if i still have it.

                  When i was 15,in auto shop class there was an awesome textbook,
                  Would come in handy for situations like this.all theory and operation.
                   
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                  • ScamperTom

                    ScamperTom Well-Known Member

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                    I’ll definitely give the service manual a close read. I have a friend who is a great mechanic so maybe he can oversee the operation. In any case I don’t want to do this twice (or die!) so I’ll make sure to do it right.
                     
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                    • Mattax

                      Mattax Just the facts, ma'am FABO Gold Member

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                      • Thanks! Thanks! x 1
                      • ScamperTom

                        ScamperTom Well-Known Member

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