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Thread: Brake bleeding on a 70's school bus?

  1. #1
    Member Rock_skipper's Avatar
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    Default Brake bleeding on a 70's school bus?

    This thing has two bleeder valves on each wheel.

    I've searched the web and came up with a couple of answers of how to do this, just wondering if any of you out there have had any experiance first hand on how it is done. Thanks for any info.

    Do you do both on the same tire and move on,, or do you do one and make the rounds before you hit the secound one?

    Its been sitting for about 30 years and the brake peadal goes to the floor. Had good brakes before it was parked.

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    Supporting Member iofthetaiga's Avatar
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    You're going to need to get the brake circuit to hold pressure before you'll have anything to bleed. When the pedal goes clear to the floor, does it generate even the least bit of resistance? Does the fluid reservoir have anything in it? I would guess the likelihood is high that the master cylinder core is rotted out and/or one or more brake lines has rotted out or been chewed through by rodents over the years...
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    Quote Originally Posted by Rock_skipper View Post
    Its been sitting for about 30 years and the brake peadal goes to the floor. Had good brakes before it was parked.
    I would replace every rubber part in the brake system before I started adding all new brake fluid.

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    Member Rock_skipper's Avatar
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    Thanks for getting back to me Io>

    The reservior holds fluid, no breaks in the line, no leaks.

    I just tried this by myself with a stick, lol, <fill the reservoir and open the valve, pump the brake then put the stick in to prop the pedal to the floor then close the valve> Did this all the way around and got fluid out of all bleeders, but still have no brakes.

    I realize that this is a two man job ,(grins) but I thought I would at least get a little bit . ( no such luck)

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    Member Rock_skipper's Avatar
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    Mc. are you talking about the master cylinder? She pumps fluid out just fine, but just seems like a lot of air in the lines.

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    I have seen videos of people who use pressurized weed sprayers and a converted cap (search youtube) to create a constantly pressurized system that allows one person to bleed brakes more easily. Granted, this is on a car so it might not work as well on a bus. As you are doing this, and with a helper it will go faster, but have you gotten to where you are seeing new fluid come though the bleed valves?

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    Supporting Member iofthetaiga's Avatar
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    1st question that needs answered: Can you pump the brake and develop pressure, or does the break continue to go to the floor?
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    Member Rock_skipper's Avatar
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    P1010525.jpgI'll have to look into that colone100. Thanks., ( yes the new fluid is coming out )

    The thing drives nice and this and the turn signal is the only thing that stops me from crusing around the state.
    Attached Images Attached Images

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    Member Rock_skipper's Avatar
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    She goes to the floor every time.

    I think I will have to get some help on this, thanks for the posts all.

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    Member Rock_skipper's Avatar
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    Took me all summer to do that. smiles.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Rock_skipper View Post
    Quote Originally Posted by iofthetaiga View Post
    1st question that needs answered: Can you pump the brake and develop pressure, or does the brake continue to go to the floor?
    She goes to the floor every time.
    If after 30 years the circuit still has fluid in it, and the reservoir is still full, but the pedal goes to the floor every time and will not hold pressure then the master cylinder is shot. Rebuild the master, as well as any/all slave cylinders, replace rubber brake lines, fill with new fluid, and bleed all air. You might get away for awhile by only rebuilding the master cylinder, but you're likely to blow out a slave or hose at a critical moment and get someone hurt. She won't be safe on the road until all the rubber in the brake system is replaced. (Sorry man. Don't shoot the messenger).

    Nice paint job!
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
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    Supporting Member iofthetaiga's Avatar
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    The good news is that it's not terribly expensive, or technically challenging. It's just a PITA.
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
    I would rather have a mind opened by wonder than one closed by belief. ~Gerry Spence
    The last thing Alaska needs is another bigot. ~member Catch It
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    Member Rock_skipper's Avatar
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    Thanks guys, < I was hoping against all odds, grins> I kinda knew that was going to be the outcome, just hoping for an easy answer, lol.

    Thanks all.
    ( just started to throw a paint job on a trailer that we pulled up here in 1964, man this thing is rough, lol, shes been sitting for 30+ years also. Its built out of a late 40s-early fifties pickup bed.) wish me luck.

  16. #16

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    Rock Skipper I am a retired school bus mechanic with 30 years of doing this. If the master cylinder was not full of fluid when you started you will need to bleed it before you start on the lines. The reason you have 2 bleeder screws on each wheel is you have 2 wheel cylinders on each wheel. One for each brake shoe. Most parts stores sell a brake bleeder that you remove the bleeder screws one at a time and screw a plug into these holes that is attached to the bleeder. You then pump your lines full back to the master cylinder. If there was a lot of air in the lines you might not get it all out in one day. Bleed it as best as you can then let it set until the next day and bleed it again. Seems like what air is left in the lines will settle to a location over night and bleed out better the next day. If you need more information pm me.

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    Pm sent. Sorry I did not see your message sooner.

  18. #18

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    Rock skipper I sent you a reply to your pm. Have not heard back and wondering if you got it. If you still need help post here and I will try to help you if I can.

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    Member Rock_skipper's Avatar
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    Sorry Cast, Between the holiday and other things, kinda got off on another project, lol. ( the summer project in the GD forum ) I still would like to have the help when I get back to that project.

    I got to sell some stuff around here so what was supposed to start out as a litte platform has turned into a bridge to nowhere, lol.

    I'll get back to you as sone as this bridge has gotten done kicking my ass, lol. Thanks.

    ( Did'nt get the P.M. )

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    Not to hijack, but I have a quick question.....When you have to pump the brakes to pressure them up enough to stop the vehicle, does it usually always mean the master cylinder is shot?
    Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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