1. Markuscurillious

    Markuscurillious Well-Known Member

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    on my 73 scamp it’s kinda hard to push the brake pedal down and damn near through the floor and when I aggressively hit them the wheels lock up...wondering if there is anyway to fix this like changing he master cylinder? I do think they are power brakes disc in the front drums in the back thx!
     
  2. Murray

    Murray FABO Gold Member FABO Gold Member

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    Is it power brakes or not? Is the motor running when you do this?
     
  3. pishta

    pishta I know I'm right....

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    sounds like bad M/C seals? a quick mash and they will lock up, a slow sink is an M/C. Even a P/B will work the brakes in a failsafe mode.
     
  4. Markuscurillious

    Markuscurillious Well-Known Member

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    yeah i think, it's got that big ufo lookin thing next to the fire wall right?


    whats a p/b?
     
  5. pishta

    pishta I know I'm right....

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    power brakes. The big taurus is a vacuum amplifier that uses engine vacuum to 'pull on' the brakes to assist in the pedal. It has a mechaincal linkage to prevent all out loss of brakes due to vacuum loss or engine stopping. Think of the brake pedal rod pushing on a switch in the PB unit that bleeds vacuum into the side of the diaphragm that allows the diaphragm to move toward the M/C. That is your brake assist. if the vacuum is not present, the brake rod just pushes on a stop just past the point of activation and its a direct link to M/C piston. a brake that sinks the floor is usually an M/C
     
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    • Markuscurillious

      Markuscurillious Well-Known Member

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      Oh okay so change that out? Damn good thing I’m going home this week gunna try and get that all worked out I’ll post pics of how things are going!
       
    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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      Could be multiple problems,
       
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      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        Start with identifying the brake system your car has.
        Also try to identify which wheel or wheels lock up.
        Lock up caused by rapid hard application of the brakes is normal in some circumstances. So keep track of the exact situation the wheel or wheels locked up under.
        Do a visual check. Start with condition of the fluid in the master cylinder. Then check the brakes on each wheel.

        Factory options on a '73
        upload_2020-1-7_18-15-12.png
        from The 1970 Hamtramck Registry - 1973 Dodge Dealership Data Book - Dart
        The 1970 Hamtramck Registry - 1973 Plymouth Dealership Data Book - Valiant/Duster

        If you find larger diameter front drum brakes, that was a running change. See the service bulletin under brakes
        The 1970 Hamtramck Registry "1973 Plymouth, Chrysler & Imperial TSBs" Page

        Service manual for '73 Dodge (can use as substitute for Plymouth FSM)
        MyMopar - Mopar Forums & Information - Service Manuals

        Chrysler Master Tech videos and booklets.
        Master Technician Service Conference - Chrysler's Training for Mechanics
        same in a different format
        MyMopar - Mopar Forums & Information - Browser MTSC by Topic - Brakes
         
        Last edited: Jan 7, 2020
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        • oldkimmer

          oldkimmer FABO Gold Member FABO Gold Member

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          Have u checked the brake fluid in the master cylinder yet? Kim
           
        • slantsixdan

          slantsixdan =..=

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          Which wheels lock up? All four, just the fronts, just the rears? The disc brake A-bodies had problems with early/easy rear lockup. The car magazines bitched about it, and so did Consumer Reports; it's a real thing. Chrysler could have fixed it for $0.00/car, but chose not to; fortunately the fix they should have done is still possible and cheap; see here.
           
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          • Markuscurillious

            Markuscurillious Well-Known Member

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            Yeah I think so, I read on (yeah!) the slant six that they could of fixed it but didn’t (maybe so they make money of after marked parts ‍♂️) but yeah it’s like when I have to make a not even that abrupt of a stop I find my self sliding and it’s fuckin scary I though my girlfriend was gunna faint haha, also is it normal for the break pedals to be so hard to push down it’s like there’s no medium it’s either pretty much coast to a stop or weeks lock up and sliding to ultimate demise
             
          • jas0162

            jas0162 Well-Known Member

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            Not trying to be an ass, but a period once in a while would make your posts much easier to understand. Stop driving your car and fix it. Have you adjusted the rear brakes? Have you jacked it up, taken a wheel off and looked at anything? Have you blead the system? You could have more than one problem, but it sounds like a new master cylinder may be in order.
             
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            • oldkimmer

              oldkimmer FABO Gold Member FABO Gold Member

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              u more than likely need a brake booster also, or maybe the hose is off or plugged. Does it have 4 inch bolt pattern or 4 1/2 in pattern? Post some pics b4 u kill urself and someone else. Kim
               
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              • Markuscurillious

                Markuscurillious Well-Known Member

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                Yeah...cause I like to drive it in the snow. But yeah I’d think it’s the master cylinder



                Geez thought this was a Chrysler forum not grammar class



                I think 4 1/2, idk I’m going home this weekend I’ll snap some pics, I just come on here to keep the sparks goin. And keeping my motivation!!!

                is that enough punctuation for ya?
                 
              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                It sounds to me like the fronts are NOT working. Easy to figure out
                 
              • oldkimmer

                oldkimmer FABO Gold Member FABO Gold Member

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                Apparently he hasn’t checked the fluid either. It’s not rocket science. Kim
                 
              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                Well , Ima thinking the fluid in the fronts is not moving. And the shoes in the back are adjusted OK. This gets you a hard pedal and rear brakes only. Since the rears are proportioned, you don't get a lotta stopping power, so you gotta press really really hard, and then, I'm guessing the booster finally wakes up and KaBlam! I have simulated this with front hoses clamped.

                If the front chamber was drained, you would have a really long pedal travel before the rear brakes came on line, and since the booster is then engaged, you would again have normal modulation, just with super reduced braking power.

                If both front caliper pistons were seized in the calipers, then the fluid would not be moving. But Both is highly unlikely
                Same if the front piston in the M/C was seized, but again highly unlikely.

                My guess is that the front hoses are internally collapsed or otherwise blocked, OR
                the line from the master to the P-valve is plugged,
                OR the C-valve is seized

                All of these situations should have turned the brake-warning lite on in the dash.
                 
              • Markuscurillious

                Markuscurillious Well-Known Member

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                hey thanks! Just got back home now gonna take a look, hopefuly get the transmission dropped, and maybe get that dash speaker in and snap some more pics. Super stoaked for this weekend
                 
              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                I'm super stoked for this weekend too; my grandkids went home, so I'm gonna nap some of it away.
                 
              • oldkimmer

                oldkimmer FABO Gold Member FABO Gold Member

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                Good 4 u AJ. A little nap never hurt anybody. Kim
                 
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