Brake fluid flush, what do you do?

Brakes for your Classic Mopar

  1. Dana67Dart

    Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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    So I found a leaking rear wheel cylinder, my master seeped some time in the last 7 years into the interior ( probably after setting for 4 years in the garage at my dad's house) but is good now.

    I have a fresh master and new rear wheel cylinders.

    I want to flush the system before reaching the 3 parts.

    I have done it the old fasion way, down, hold, open, close, up, repeat till clear fluid runs out (keeping the resivour full the whole time)

    Thought about having it power blead at the local shop, ($80.00 ouch)

    What do you all do?
     
  2. toolmanmike

    toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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    I usually don't have a helper or a power bleeder. After all the fixing is done , fill the master and open just the passenger rear bleeder and wait patiently until the fluid starts running. close that bleeder and go to the drivers rear. Then to the RF and finally the LF. Make sure your keep the fluid full.
     
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    • Dana67Dart

      Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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      I thought you couldn't gravity bleed rears?
       
    • toolmanmike

      toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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      Sure you can.
       
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      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        I dislike NOT pressure bleeding, and you can (most of the time) fairly easily build something that will work. If you can keep your eye on the master you don't even need something to feed fluid. On the older cars such as these, you need a flat plate and gasket. You can make this even out of plywood. "Rig" a way with say, eyebolts/ J bolts (2 or 4) and a light piece of chain to clamp the plate to the top of the master. Piece of whatever for a gasket, bulk neoprene rubber. cut/ gouge a channel in the plate to carry pressure to the two sections, and tap the thing for some sort of air fitting. Buy a cheap regulator

        One "can" I built........found an aluminum drinking bottle at the thrift with a substantial screw in lid. Bought a length of 3/16 or 1/4 brake tube and a basic end fitting from inverted flare to pipe Drill to holes in the screw cap of the water bottle, use JB weld to glue the tubing in, one just enter, the other to the bottom

        Now you can "series" that bottle in your air system to the pressure plate device and it will auto feed fluid

        Use lots of rags and a cheap baking/ etc pan to catch leakage. Thrift store towels are cheap. You don't want fluid on your paint

        I've done this with just about every vehicle I've needed. On the Dakota/ ram/ GMC I bought replacement filler caps at the parts store, drilled and tapped the cap for a fitting and away you go. The caps run ?? 12-15 bucks

        The general idea this is a GM guy's method I stole from the www

        bleeder.jpg
         
        Last edited: Sep 21, 2020
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        • pishta

          pishta I know I'm right....

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          Gravity bleed will work the same way you you can siphon gas up and out of a tank. If the fluid is flowing, the siphon action will keep it moving. The California Aqueduct is built on this principle to get water over portions of the 4100 foot Tejon Pass. As long as there is fluid in the reservoir and no air bubbles, the fluid will pull itself through the system to a lower level.
           
        • Dana67Dart

          Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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          My recollection was that the rear system has the residual pressure valve and that prevents gravity bleeding. I have never tried gravity bleeding so I'm going to give it a try.

          My 1st priority is to put a pint of fluid through my 53 year old brake system.
          Then change the parts, then some more flushing and a final bleed.
           
        • pishta

          pishta I know I'm right....

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          10 psi RPV's just 'check valve' hold some back pressure to maintain the cup to wall integrity. If you pump the brakes, you set the 10 and you should be able to crack the bleeder and get a little squirt, but its a check valve to prevent a back flow. Once the bleeder is cracked the pressure is off the RPV , it will relax and gravity will pull fluid forward through that toward the brake cylinder. I believe this is how those work. It takes 75 PSI to overcome the drum brake return springs!
           
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          • flingdingo

            flingdingo Well-Known Member

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            I just hook up my pressure bleeder and go to it. Know any mechanics? Most of them own one. Maybe a buddy would be willing to do it for the cost of a couple drinks.
             
          • Big_John

            Big_John In my defense, I was left unsupervised.

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            I bought a pressure bleeder last year and wonder now why I didn't buy one years ago. $65. Cheaper than the $80 for the shop, so it's just paid for itself and you have it for the next time.

            Just have to supplement the chains with a C-clamp on the master cylinder.

            https://www.amazon.com/gp/product/B00CJ5DY16/?tag=fabo03-20


            81s3pPyL2eL._AC_SL1500_.jpg
             
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            • BobW

              BobW Curmudgeon At Large FABO Gold Member

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              I use a Mity-Vac to pull the fluid out of the master, then fill with fresh fluid and pull through each corner. Once I have clean fluid at all four bleeders, I have the wife do a final pedal bleed, usually just one or two pumps at each bleeder to be bubble free and firm.
              I've used this same Metal Mity-Vac for 30+ years!
               
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              • hwd2

                hwd2 Well-Known Member

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                Remember there is a difference between gravitation and siphoning. The former will usually work for most vehicles because the reservoir is the highest point of the hydraulic braking system. Once you open a bleeder, liquid must eventually travel thru the system - assuming no blockages or restrictions. Siphoning requires a 'sealed passageway' (ie: tubing) to allow fluid (ie; gasoline) to travel uphill - - before it moves back down (yes, with some gravity assist) to exit at a point that must be lower than originating supply vessel. In other words, the 'tubing' length from entrance to 'summit' must be shorter than the section from 'summit' to exit - in order for siphoning to take place.
                 
                Last edited: Sep 22, 2020
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