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Thread: A Brake Diaphram

  1. #11
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    I don't think anybody can paint a clearer picture than Darl just did. Our coaches have to be respected and I can think of a number of things as owners who work on them we have to be aware of.

    Obviously spring brakes must be respected. But if you are contemplating getting under the coach make absolutely certain it is properly supported under the chassis support points. It doesn't matter if you are merely going to be under it for a second or two. Don't do it without the coach being supported.

    Stay away from exposed belts when the engine is running. You will not stand a chance if you wear loose clothes and get caught in a belt.

    Don't under any circumstances work on an inverter unless you are 100% sure you have removed not only 120V power, but the 12 or 24 volt circuit to the batteries has been disconnected.

    I'm sure others can suggest more things to be aware of, but those leap out at me as biggies.

  2. #12
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    I just stumbled across this thread looking for an oldy to revisit. He is lucky he didn't kill himself.

    Let's go deeper.

    20180613_192732.jpg

    A modern maxi looks like this. 1 clamp that's removable for the service diaphragm and 1 that's not for the bigger emergency brake spring I'm pointing.

    20180613_115539.jpg

    20180613_192742.jpg

    Here is an old style where both chambers and diaphragms can be opened and repaired.

    The main spring can kill u back when there where bad consiquenses for stupid decisions.

    I've seen this type on Prevo and I'm quite confident there r still a few out there on late 80s stuff.

    I will rebuild these, both ends, when I see them, because u can for less than 20 bucks instead of replacement.

    I'll open one up and uncage it open far enough so u can see the difference between the main spring and the service brake spring.
    Last edited by Joe Camper; 06-13-2018 at 08:55 PM.
    1990 Peterbuilt 377
    3406 B Caterpillar
    9 Speed Roadranger
    708 243 7871

  3. #13
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    Let's have a caging a chamber and removing a diaphragm 101

    20180613_154716.jpg

    20180613_161444.jpg

    20180613_161122.jpg

    Here is the caging tool and where it goes. It gets twisted after inserted then tightened all the way down.

    20180613_161138.jpg

    2 good tips here. First if u release the emergency brake first air pressure does most of the work u only have to crank down the last few turns manually. Also the threads go deeper than a deep well will go and this rachet with hollow sockets works great here.
    1990 Peterbuilt 377
    3406 B Caterpillar
    9 Speed Roadranger
    708 243 7871

  4. #14
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    Mar 2013
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    Chicago
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    Only half way there.

    20180613_154529.jpg

    When u first start backing the brake off by depressing the lock ring on the 9/16 adjuster nut the slack does not move. The shaft turns only.

    20180613_154539.jpg

    When the cams, not visible, bottom out on the brake shoe rollers, not visible, u will feel that for sure. Then keep going and the slack adjuster will move outward.

    20180613_154558.jpg

    The slack pulls the pushrod that squeezes the smaller service brake spring and when u install the new diaphragm there is no struggle.



    20180613_161416.jpg

    Another thing. Only between the clamps is there 2 seporate pressurized chambers. The emergency half that is energized only when u release the parking brake and the service side that is only energized when u r using the brakes for stopping. Outside the 2 diaphragms and clamps is open to atmosphere. If your unfamiliar with chambers and u want to verify what line is service and what is emergency the ports r not lined up and clearly visible what line is going to what half the chamber. In the photo the left line is feeding the serice brake side and the right one is emergency air.
    Last edited by Joe Camper; 06-14-2018 at 09:35 AM.
    1990 Peterbuilt 377
    3406 B Caterpillar
    9 Speed Roadranger
    708 243 7871

  5. #15
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    20180613_132959.jpg

    Now I've removed the service brake clamp and with a tap the 2 pieces seporate and the diaphragm comes out.

    In the photo I've turned the slack adjuster back to release the service brake sprint so u can see it.

    Nother good tip. If u don't hold the spring down by backing the slack out first u r faced with trying to push it back during diaphragm instalation and it's much more difficult. When u push on this plunger u r not just compressing IT'S spring u r also having to overcome the springs that hold the brake shoes to the rollers. It's doable but unnessessary, do it my way.

    20180613_132318.jpg

    Now here is the emergency half opened up, again these r the old style very dangerous I'm showing this because I thought u might want to see and I know what I'm doing.

    If u zoom in the middle u can see how the cage tool locks in from the back side.

    20180613_133436.jpg

    Here is the emergency half open with the diaphragm no longer present and I backed the cage bolt out as far as I could so that main spring is exposed.
    Last edited by Joe Camper; 06-14-2018 at 09:39 AM.
    1990 Peterbuilt 377
    3406 B Caterpillar
    9 Speed Roadranger
    708 243 7871

  6. #16
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    20180613_155125.jpg

    Before u loosen these clamps note where the nuts r so u know how tight is tight. I take only 1 turn from 1 nut and the other completely off and it comes free. This makes reassembly better.

    20180613_155143.jpg

    So y put the diaphragm up and rest the clamps like in the photo before lifting the chamber back up.

    20180613_155230.jpg

    Then put the chamber up with 1 hand and bring the clamp into place with your other hand. Mild blows with a hammer while squeezing the open end of the clamp brings the 2 half's close enough togeather to get the nut and bolt started.

    20180613_155624.jpg

    20180613_160038.jpg

    2 last tips first before u go for the slack adjuster and release its return spring and adjust the brake, it's a good time to grease the s cam shaft. U got it almost 180 from where it normally sits when the slack is backed out. I'm pointing to that grease fitting for the S cam shaft.

    Now go back to the adjuster on the slack and let the slack walk back, when it stops moving continue on the adjuster until u then begin to push the shoes outward and tighten down till the adjuster nut stops. If tight u cant turn the brake drum at that point u r bottomwd out the brake is tight . Then about a 1/4 turn back from tight is where I put the 9/16 bolt for the slack. pull the slack to check it. Make slight adjustments to feel if nessessary.

    The less slack the better, however if u want them all equal and if 1 hub requires additional slack to release the drum sufficiently the rest need to be loosened to match its slack.

    And that's it. How to cage a brake replace a diaphragm and a look at a old style chamber and it's main spring exposed.

    Where else do u get this stuff?
    Last edited by Joe Camper; 06-14-2018 at 09:59 AM.
    1990 Peterbuilt 377
    3406 B Caterpillar
    9 Speed Roadranger
    708 243 7871

  7. #17
    Join Date
    May 2012
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    Joe knows his stuff.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

  8. #18
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    Jun 2017
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    Spencerville
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    Holy Moly! I was just doing some research and I am really happy I checked out this thread! I had no idea of the danger and certainly won’t attempt this on my own.... so, I guess this really does make my phone call to Joe Camper all the more valid!
    Michael
    1981 Le Mirage 40’ “Charlotte”

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