Pedal gets hard half way down, little front brakes

Discussion in 'Brakes for your Classic Mopar' started by Lvlrlvlopar, Sep 15, 2018.

  1. Lvlrlvlopar

    Lvlrlvlopar New Member

    Messages:
    3
    Likes Received:
    0
    Joined:
    Sep 15, 2018
    Location:
    Albany
    Local Time:
    4:20 PM
    Hi I’m having some trouble with my car 1970 dart 4 wheel drum. I recently had the front end apart for about a month rebuilding it. The drums were off the whole time. Finally got it back together and now my front brakes don’t seem to be doing much. The rear tires lock up first and the pedal seems to get hard half way through travel. I readjusted the front shoes. Gave it a quick bleed at the wheel cylinders. And cracked the lines at the master loose. I did get a couple bubbles from the line going to the front brakes. But the only thing that helped any was re adjusting the shoes. Still locking up the rear tires and only slight nose dive and have hard pedal half way down. 12” vacuum at idle. Thought the hoses may have gotten collapsed internally but they seemed to bleed ok. Is it possible my master cylinder went bad while sitting? Or the hoses are bad but bleed ok? I was going to take the drums off next and check wheel cylinder movement. How much travel should I expect? Any other ideas?
    Thank
     
  2. SGBARRACUDA

    SGBARRACUDA ROY FABO Gold Member

    Messages:
    12,759
    Likes Received:
    2553
    Joined:
    Dec 7, 2006
    Location:
    PLANT CITY FL.
    Local Time:
    4:20 PM
    Problem may be rear shoes wet from brake fluid leak or rear end 90w soaking them. That will cause the rear to lock up. You may want to look at front wheel cylinders, they may be cruded up and pistons not moving much.
     
    • Agree Agree x 1
    • el5dart

      el5dart Well-Known Member

      Messages:
      85
      Likes Received:
      26
      Joined:
      May 16, 2018
      Location:
      memphis, tn.
      Local Time:
      3:20 PM
      this may not help you. i was stumped on why my front left drum keeps locking up. took it apart 3 times, replaced wheel cylinder and that didnt fixit. i think ive narroed it down to the brake hose being collapsed.
       
      • Agree Agree x 1
      • BigBlockMopar

        BigBlockMopar BigBlockMember

        Messages:
        1,478
        Likes Received:
        427
        Joined:
        May 1, 2011
        Location:
        Netherlands
        Local Time:
        10:20 PM
        Swapped lines front/rear on the MC by any chance?
        With 12" vacuum on the engine I would do an engine tune-up first. That's lousy vacuum and it's probably struggling to pull the booster for brake-assist.
         
      • SGBARRACUDA

        SGBARRACUDA ROY FABO Gold Member

        Messages:
        12,759
        Likes Received:
        2553
        Joined:
        Dec 7, 2006
        Location:
        PLANT CITY FL.
        Local Time:
        4:20 PM
        With the cam that is in my Dart, the best I can so is 12" vacuum. But that has always been enough to operate my power brakes. Only difference is I have Disc/Drum.
         
      • j par

        j par Well-hung Member

        Messages:
        8,910
        Likes Received:
        2692
        Joined:
        Jul 2, 2014
        Location:
        Portland Oregon
        View My Photos
        Local Time:
        1:20 PM
        Would a week booster make the back brakes lock up first? That doesn't make sense.
        And if I read correctly you took the lines off at the master cylinder? Would that create another bubble? It seems to me it's either a wheel cylinder or it still needs to be bled more. Could be a bad master cylinder, could be in the proportioning valve.
         
        • Agree Agree x 1
        • inertia

          inertia Well-Known Member

          Messages:
          2,967
          Likes Received:
          330
          Joined:
          Feb 4, 2011
          Location:
          Victoria B.C. Canada
          View My Photos
          Local Time:
          1:20 PM
          Re-bleed the front brakes.
           
          • Agree Agree x 1
          • dartfreak75

            dartfreak75 Well-Known Member

            Messages:
            699
            Likes Received:
            188
            Joined:
            Aug 10, 2011
            Location:
            Virginia
            Local Time:
            4:20 PM
            I know from experience that bad wheel cylinders will make drums lock up easy. If it where me I would inspect your shoe travel vs each side if one is moving more than the other that could indicate a bad hose. And double check your bleeding. Did you bench bleed the master cylinder? If it's been setting for months with no fluid it probably won't hurt to bleed it.
             
          • grjammer

            grjammer LIMONADE FABO Gold Member

            Messages:
            571
            Likes Received:
            50
            Joined:
            Aug 14, 2013
            Location:
            PA
            Local Time:
            4:20 PM
            sounds like the proportioning valve or master is connected wrong. since you had it apart I would start there. If you drained the master while doing the work you may need to bleed it then the front brakes again.
             
          • SGBARRACUDA

            SGBARRACUDA ROY FABO Gold Member

            Messages:
            12,759
            Likes Received:
            2553
            Joined:
            Dec 7, 2006
            Location:
            PLANT CITY FL.
            Local Time:
            4:20 PM
            The place to start is jack the car up on jack stands. Get someone else to apply the brakes while you attempt to turn each wheel by hand.
             
            • Agree Agree x 1
            • Murray

              Murray FABO Gold Member FABO Gold Member

              Messages:
              508
              Likes Received:
              207
              Joined:
              Apr 19, 2010
              Location:
              San Jose, California
              Local Time:
              1:20 PM
              M/C problem.
               
              • Agree Agree x 1
              • Murray

                Murray FABO Gold Member FABO Gold Member

                Messages:
                508
                Likes Received:
                207
                Joined:
                Apr 19, 2010
                Location:
                San Jose, California
                Local Time:
                1:20 PM
                Or distribution block off-center.
                 
                • Agree Agree x 1
                • dartfreak75

                  dartfreak75 Well-Known Member

                  Messages:
                  699
                  Likes Received:
                  188
                  Joined:
                  Aug 10, 2011
                  Location:
                  Virginia
                  Local Time:
                  4:20 PM
                  Yea I agree with this.
                   
                • Lvlrlvlopar

                  Lvlrlvlopar New Member

                  Messages:
                  3
                  Likes Received:
                  0
                  Joined:
                  Sep 15, 2018
                  Location:
                  Albany
                  Local Time:
                  4:20 PM
                  Brake lines were not taken off or empty during the time I was doing new bushings and ball joints. I did suck the master out and re fill with fresh fluid after I noticed the brakes weren’t working like they did. After that is when I bleed the brakes. The next day is when I cracked the lines on the master loose. Now that I think about it the air I saw when loosening the line on the master could have been because the first line I cracked it loose I didn’t have any pressure on the pedal because I wasn’t sure it would come loose. I retightened it and the. Had pressure on the second time I cracked it loose. The second line I had pressure on the pedals hen I initaly loosened it. The front wheels would turn by hand when brakes were depressed before adjusting the shoes. Afterwards they would not. I did not check how the rear wheels turned by hand. How would the distribution block play into this? Isnt it only to split fluid for front wheels and give a warning light if you loose pressure on either the front or rear lines? I did think about that and am going to ground out the wire to make sure that the wiring to it works properly. Then I will check shoe travel and rebleed then compare travel again and test drive.
                  Thanks
                   
                • Murray

                  Murray FABO Gold Member FABO Gold Member

                  Messages:
                  508
                  Likes Received:
                  207
                  Joined:
                  Apr 19, 2010
                  Location:
                  San Jose, California
                  Local Time:
                  1:20 PM
                  When you have uneven pressure between front and back, you risk activating the rod in the distribution block. You are imitating a M/C failure. That is what they are designed to do. It is just doing it's job.
                   
                • AJ/FormS

                  AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

                  Messages:
                  13,788
                  Likes Received:
                  3346
                  Joined:
                  Jan 19, 2014
                  Location:
                  South-Central Manitoba,Canada, 900ftelevation
                  View My Photos
                  Local Time:
                  3:20 PM
                  Clues in color, click to expand

                  This is a toughie
                  but you supplied some great clues;
                  The hard pedal seems to indicate that the hydraulics are OK, keyword "seems"
                  The halfway down tells me it could be a slack-adjuster adjustment problem
                  The rear lock-up seems to confirm this
                  But the statement about having adjusted the front shoes already is a bit of a puzzler
                  So I'm gonna guess that the front wheel cylinders are running out of piston travel, and hitting a mechanical stop, before pushing the shoes out, or just not moving far enough in the first place. The latter could be because the pistons inside the master are not hydraulically linked,and the front system is actually waiting for the rear to link up mechanically. Thus,it is operating in failure mode.
                  I suggest to watch the compensating ports one in each reservoir, while a helper slowly applies the brake-pedal,holds it when it gets hard, and then slowly releases it back to the start....ALL the way.. You should see the fluid roiling at the beginning of the application, and a more roiling at the very end, as the fluid returns;watch out for a geyser at the end . If there is any air in the system it will cause the fluid to return in a hurry, and the geyser is the proof of it. I have seen the geyser hit the hood, so protect your paint accordingly, and make sure your helper knows to stop when you yell STOP !!!!!!!! There must be roilings or geysers to prove the C-ports are open. Without compensation, there might not be enough fluid moving out to the Wheel Cylinders to affect meaningful brake action.
                  Ok so assuming the ports are both open,or that you have mechanically opened them; then I recommend to bench-bleed the M/C, to fill the inter-piston area with fluid. Sometimes/usually, you can get away with doing this on the car. But in your case,you may have to lower the front of the M/C , lower than the rear.
                  That's all I got
                   
                  Last edited: Sep 17, 2018
                  • Like Like x 1
                  • Lvlrlvlopar

                    Lvlrlvlopar New Member

                    Messages:
                    3
                    Likes Received:
                    0
                    Joined:
                    Sep 15, 2018
                    Location:
                    Albany
                    Local Time:
                    4:20 PM
                    I think I have it all set. The master cylinder was leaking a little bit when I pulled it off the booster. That must be where the air came from. Also someone was in there before and the aluminum spacer plate was upside down and backwards and got cracked. I think because when they tried to put it on right the plastic piece that holds the air filter didn’t have the cutouts for the retainer screw and tab. The rear shoes needed to be adjusted up a little too. It still doesn’t lock up the front right. I am going to try to bleed it again but I think it’s the adjustment is a little loose. I left it this way because there is some runout in the drum. Anyone make a decent drum or should I get these turned if there’s meat on them.
                    Thanks again for all of your help guys.
                     
                  • SGBARRACUDA

                    SGBARRACUDA ROY FABO Gold Member

                    Messages:
                    12,759
                    Likes Received:
                    2553
                    Joined:
                    Dec 7, 2006
                    Location:
                    PLANT CITY FL.
                    Local Time:
                    4:20 PM
                    If you were closer I would turn them for you. I have a Amco 4000 brake lath with all the tooling.