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Brakes Gone
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akherber



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    Post: #1
    Brakes Gone

    Now this is a amateur diagnosis but I believe I lost my Master Cylinder Friday night. The pedal, with intermittent and often minimal resistance would push all the way to the floor. As of Saturday morning after the car reached operating temperature there was absolutely no resistance to the pedal. Brakes are in an "on or off" application. So I can push the pedal to the floor and it is a matter of pressure and a difference of about 1/4" that applies (constantly locking the rear passenger drum up) the brakes.

    Now for my initial reactions:
    I checked the cylinder reservoir and there is fluid present and nearly full.

    The two rear drum cylinders are not leaking neither are the connections at the front disks.

    I replaced the vacuum check valve (because I can handle 5.99)

    On the recommendation of a guy at the cruise night last night, I went over the vacuum booster and all hoses with some water to listen for vacuum leaks but none revealed themselves.

    So from what I know. Master Cylinder goes out, the pedal will hit the floor. The master cylinder is on order from NAPA.

    What I need to know: How can I test my vacuum booster for proper operation? When I replace the master cylinder will I "know" that it was the issue? Do the brakes become unmanageable when there is no vacuum booster and could these symptoms be a bad booster instead?

    Thanks in advance.
    Offline 11-14-2010 06:33 PM
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    Tnfastbk



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      Post: #2
      RE: Brakes Gone

      (11-14-2010 06:33 PM)akherber Wrote:  Now this is a amateur diagnosis but I believe I lost my Master Cylinder Friday night. The pedal, with intermittent and often minimal resistance would push all the way to the floor. As of Saturday morning after the car reached operating temperature there was absolutely no resistance to the pedal. Brakes are in an "on or off" application. So I can push the pedal to the floor and it is a matter of pressure and a difference of about 1/4" that applies (constantly locking the rear passenger drum up) the brakes.

      Now for my initial reactions:
      I checked the cylinder reservoir and there is fluid present and nearly full.

      The two rear drum cylinders are not leaking neither are the connections at the front disks.

      I replaced the vacuum check valve (because I can handle 5.99)

      On the recommendation of a guy at the cruise night last night, I went over the vacuum booster and all hoses with some water to listen for vacuum leaks but none revealed themselves.

      So from what I know. Master Cylinder goes out, the pedal will hit the floor. The master cylinder is on order from NAPA.

      What I need to know: How can I test my vacuum booster for proper operation? When I replace the master cylinder will I "know" that it was the issue? Do the brakes become unmanageable when there is no vacuum booster and could these symptoms be a bad booster instead?

      Thanks in advance.

      If the booster goes out your brakes will be harder to push than if they were manual brakes.
      Offline 11-14-2010 06:49 PM
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      c9zx


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        Post: #3
        RE: Brakes Gone

        I agree with Tnfastback. Does it have the same brake fluid in the system it had when you bought the car?
        Offline 11-14-2010 07:54 PM
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        akherber



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          Post: #4
          RE: Brakes Gone

          (11-14-2010 07:54 PM)c9zx Wrote:  I agree with Tnfastback. Does it have the same brake fluid in the system it had when you bought the car?

          I wouldn't know. Being the smart consumer, the first day I had it I changed the fluids (oil, coolant, brakes, rear-end, transmission). I discovered the two rear cylinders were completely frozen so I replaced them as well. The brakes were done professionally since I don't trust myself that much.
          Offline 11-14-2010 07:58 PM
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          Hemikiller



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            Post: #5
            RE: Brakes Gone

            If both reservoirs are full, then you have a bad master. Been through that exact same scenario several times, with the last 1/4" travel locking the rears...
            Offline 11-15-2010 07:46 AM
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            Widowmaker00



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              Post: #6
              RE: Brakes Gone

              I got a brakes question, I had a master cylinder that would leak badly from the cap, so I changed the cap. Still leaked. So I changed the master cylinder, bench bled correctly, and the new one did the exact same thing. The brakes after being bled will stay pumped up for a while but eventually (a day or two) will go all the way to the floor.

              There are no leaks in the system other than the master cylinder.

              Eventually the car will get an entirely new brake system anyways, but until then I would like the car to stop lol.
              Offline 11-15-2010 08:35 AM
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              akherber



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                Post: #7
                RE: Brakes Gone

                (11-15-2010 07:46 AM)Hemikiller Wrote:  If both reservoirs are full, then you have a bad master. Been through that exact same scenario several times, with the last 1/4" travel locking the rears...

                This is great news! I mean to figure out what it is feels good not so much that I don't have brakes... Now the part is on order already and hopefully will be here this week.
                Is the bench-bleeding process something that I (an amateur) can do? I'm pretty good at following directions and getting understanding out of what I'm doing but brakes are something I don't want to mess up.
                My thoughts are if it takes me 4 hours of my time to do the swap or a mechanic 1 hour of his, well he costs 80 dollars an hour... But if it is something that requires so decent knowledge, or should be done with special tools or another person then I might take it in.
                Offline 11-15-2010 12:56 PM
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                Tnfastbk



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                  Post: #8
                  RE: Brakes Gone

                  (11-15-2010 12:56 PM)akherber Wrote:  
                  (11-15-2010 07:46 AM)Hemikiller Wrote:  If both reservoirs are full, then you have a bad master. Been through that exact same scenario several times, with the last 1/4" travel locking the rears...

                  This is great news! I mean to figure out what it is feels good not so much that I don't have brakes... Now the part is on order already and hopefully will be here this week.
                  Is the bench-bleeding process something that I (an amateur) can do? I'm pretty good at following directions and getting understanding out of what I'm doing but brakes are something I don't want to mess up.
                  My thoughts are if it takes me 4 hours of my time to do the swap or a mechanic 1 hour of his, well he costs 80 dollars an hour... But if it is something that requires so decent knowledge, or should be done with special tools or another person then I might take it in.

                  Heres some instructions:
                  After successfully rebuilding a master cylinder (or when fitting a new one) it is a good idea to bench bleed the MC before installing it in the car. This will fill the MC with fresh air-free fluid and in effect "prime" it for integration with your car's hydraulic brake system, making your on-the-car brake bleeding a little easier.

                  The basic idea is to create mini hydraulic system on your bench. You can use old brake line fittings if you have them but I didn't so I purchased a master cylinder bleed kit from my local auto parts store. A new MC may include the necessary parts already. The kit should consist of a number of plastic fittings which are designed to fit in the outlets (usually two, front and rear) of your MC. One end of the fittings will be threaded and the other will have a round smooth hose adapter. Thread the appropriate fittings into the outlets on your MC. The kit will also contain a length of plastic hose. My kit had black hose but I found some spare clear hose and used it instead - this will allow viewing of the air bubbles passing through the hose. My kit also had a plastic clip used to hold the two pieces of hose together and clamping to the edge of the fluid reservoir.

                  Clamp the cylinder firmly in a bench vise so that the cylinder area is level. If it is pointing upwards the air will remain in the cylinder. Slide the hoses onto the fittings. Cut the hoses just long enough to reach into the reservoirs and remain submerged - the shorter the length of hose the better. Place the other ends of the hoses into the fluid reservoirs (you'll probably have hold them in place somehow because once you start pumping they'll want to flail around in the air and spray brake fluid everywhere). If you can get a helper that is ideal.

                  Fill the reservoirs with new brake fluid, and pump the piston slowly and evenly, full strokes. I used a big Phillips screwdriver because its tip doesn't damage the piston and the handle gives you something to lean against. I would not worry about the fluid getting recirculated because it is brand new and you are creating a temporary hydraulic circuit with the hoses which will not become contaminated with dirt. The air which is still in the system at this point will be bled out. Pump the cylinder until the tubing contains no more air bubbles and no new ones emerge from the MC on the down stroke. On my MC this took about 15 strokes some may require more, some less. Keep going until the air stops as this will make the task of bleeding the brakes in the car much simpler. When all the air is out, mount the cylinder in the car. Here you have to be careful to prevent the fluid still in the hoses from spaying your car and any other painted objects nearby - brake fluid is a great paint remover! If you decide to remove the hoses before installing on the car, make sure to plug up the fittings - I just held the hoses up while transferring from bench to car. Once the MC is mounted in the car, remove the fittings and connect the brake lines. You'll lose a little fluid but the check valves in the cylinder should stop any major leakage. Now you are ready to bleed the brakes in your car and it should be a lot easier than if this step was avoided.
                  Offline 11-15-2010 02:04 PM
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                  72HCODE


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                    Post: #9
                    RE: Brakes Gone

                    i ended up using a vacuum pump to prime the new master on the car, if you don't prime the master and just fill it with fluid and try to use it, it will not push the fluid out. i didn't know about bench bleeding at the time.

                    so i used my vacuum pump to basically suck the air out of the lines and pull the brake fluid through the system.

                    i switched to Dot 5 so i moved a lot of fluid through the system to completely flush it out.

                    that was 3 years ago. Just 3 weeks ago i flushed the brake system again with new fluid.
                    Offline 11-15-2010 02:17 PM
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                    Hemikiller



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                      Post: #10
                      RE: Brakes Gone

                      Bench bleeding is very easy, typically the new master will come with a bench bleeding kit. The latest ones have two plastic plugs, others have two fittings with a couple lengths of tube and a clip to hold the tubes. After using both, I prefer the plugs.

                      Clamp the master in a vice so that you can stroke the piston with a screwdriver. Do this slowly and with the lid off. Go slowly so that the fluid doesn't shoot up, out and all over your garage. Watch the ports in the base of the reservoirs. When air bubbles stop coming out, you should be ready to install it in the car.
                      (This post was last modified: 11-15-2010 02:54 PM by Hemikiller.)
                      Offline 11-15-2010 02:53 PM
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