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Thread: A Brake Diaphram

  1. #1
    Joe Cannarozzi Guest

    Default A Front Brake Diaphram

    The front brakes on ALL prevo are standard non maxi single diaphragm brake chamber. Under normal braking they may see 10 or 15 pounds of air pressure, minimal. If it should leak it will only leak when you are using the brakes.

    I have never looked here and had no idea if these were original or not so I opened them up. Good thing I did.

    Everything is pretty crusty on the surface but very clean on the inside and will easily provide many more years of service with simply a new pancake and rubber brake line.

    cockpit removal and upgrade 321.jpg

    cockpit removal and upgrade 320.jpg

    You have to check the return spring behind the plunger to make sure it is not overly corroded. This one was fine.
    cockpit removal and upgrade 312.jpg

    cockpit removal and upgrade 319.jpg

    This is not new but the inside of the original chamber.
    cockpit removal and upgrade 318.jpg
    Last edited by Joe Cannarozzi; 03-31-2009 at 10:18 PM.

  2. #2
    dalej Guest

    Default

    Great photos and post Joe!

  3. #3
    Join Date
    Apr 2006
    Location
    Battle Ground, WA
    Posts
    851

    Default

    Great post Joe. This points out the fact that when updating chassis components there is no real need to install brand new brake chambers. For the hands on folks, they come apart easily and are easily overhauled. One must be very careful however when disassembling the emergency dual brake chambers.

  4. #4
    Join Date
    May 2007
    Location
    Port St. Lucie, FL
    Posts
    1,745

    Default

    Great post, Joe.

    But I gotta ask.....

    Which job is dirtier.....tearin' em apart to re-build?..... or replacin' em?

  5. #5
    Joe Cannarozzi Guest

    Default

    Paul, Paul, Paul.

    I can't believe you even asked that question.

    I could not have been more surprised to crawl under what I defined as one of the best looking and well kept Liberty's in the club (yours), only to emerge dirtier than I have ever gotten on anyone's yet,and 2 days in a row.

    Then to add insult to injury you give me hand cleaner with enough grit to rip the first 2 layers of skin off prepping me for the burn of the gasoline you then handed me, and we hear complaints about water-boarding, sheesh.

    P1051033[2] (2).JPG

    I could not get this dirty working on our bus if I tried and it is 15 years older than yours.

    In answer to your question I guess it depends on whos I'm working on

  6. #6
    Join Date
    May 2007
    Location
    Port St. Lucie, FL
    Posts
    1,745

    Default

    I hear ya, Joe....

    Was pretty surprized myself to see how much grime one (apparently clean) bus can deposit on a guy. I think the Liberty just enjoyed your touch so much she insisted on leaving her mark

    It was fun though.......

  7. #7
    Joe Cannarozzi Guest

    Default

    If you do decide to just replace a diaphragm NEVER NEVER remove the clamp on a chamber with 2 sets of them.

    NEVER .

    Putting it another way if the chamber has only 1 air line going to it you are safe, If it has 2 air lines going to the chamber LEAVE IT TO SOMEONE WHO IS SURE WHAT THEY ARE DOING. If you pull the wrong clamps on a chamber with 2 sets of clamps it could kill you.

    Here is all it takes to relieve the tension from the spring on that SERVICE BRAKE diaphragm so you can switch it.

    I have finished up with the steer axle and I neglected showing some important steps that I can demonstrate with the tag.

    Simultaneously take a large screwdriver shove it in the cleaves of the slack adjuster and pull back with one hand (just like you were checking slack) and with your other hand clamp the push rod with some vice grips right at the housing so it can't spring back
    my bus 073.jpg

    my bus 074.jpg
    Now when the 2 clamps are removed the tension is gone.

    The 2 diaphragms on the steer were dated 1981 so that means they were not only original but sat on a shelf for 4 years before they were used. The new ones I'm installing were manufactured in 07. No good Mr. Parts guy, no good. I expect my parts deli fresh, thank you.
    Last edited by Joe Cannarozzi; 04-17-2009 at 12:09 AM.

  8. #8
    Join Date
    Jan 2006
    Location
    anytown
    Posts
    8,908

    Default

    Joe has spoken the gospel with respect to monkeying around with combo brake chambers. The spring brake portion of those brakes are under considerable pressure when not caged. However, only the older combo brakes can be serviced anymore. The spring brake portion (the emergency brake part of the combo) is permanently assembled on newer models. I don't know when the change was made but they cannot be disassembled.

    I have had a brake diaphragm failure and it was not from an aging rubber that cracked and failed, but instead was the result of a poor finish on the head of the plunger that the diaphragm pushes against. Apparently from driving in the snow belt the corrosion caused by all the salt created a rough surface that wore through the rubber creating a weak spot that failed. The failure was on the emergency brake diaphragm, and at the time I was able to rebuild the brake as Joe showed, but the spring had been caged using the T bolt supplied with the brake.

    It is not the age of the diaphragm that is likely to be the problem, but the quality of the inside of the chamber. If there is any corrosion, change the chamber, not the diaphragm.

  9. #9
    Join Date
    Nov 2006
    Location
    Reno, NV
    Posts
    291

    Default Almost got killed working on a charged air brake.

    Back in about 1962 I was pulling a set of doubles, hauling tomatoes out of the Chico Bean Growers in Northern, CA. I was a real green truck driver and when I found a brake pot on the rear axle of my rear trailer leaking I called my boss, the owner of the truck. He instructed me, by phone, to replace the diaphragm. His instructions were not that clear and did not have the warning that you guys are rightly giving readers of this forum.

    I released the air pressure to the trailer brake and replaced the rubber diaphragm. The cap was held on with a two-bolt clamp. After I charged the lines by moving the trailer brake lever full on. (that was close to 120psi) I checked the device for leaks. There was just a whisper of air so instead of draining the air lines I proceeded to use a wrench to tighten the charged pot clamp. You guessed it! I found myself 20-25 ft from the trailer in dust about 6 inches deep with my forehead split wide open and blood everywhere. When I put my hand to the wound all I could feel is a big pulpy mass which I actually thought was my brains. Some people put me in an old pickup and drove me, while I was holding my 'brains' inside my head, to the Chico Hospital. It turned out that my "brains" were just a pulpy mass of flesh where the clamp hit and and ripped everything off to my skull. After a lot of cleaning my forehead skin was reattached and stitched back in place. An xray revealed no fracture and, what the doctor said, one of the thickest skulls he had ever seen.

    After a couple of weeks of rehab I was released back to work. Because the stitches were put in properly I never needed plastic surgery.

    I know all of the jokes this little story will generate but I can tell you the best outcome. I have a tremendous respect for anything air-powered and assure you that there is NEVER a short cut when working on this equipment. Next time you see me check out the scar on my forehead that runs from the top of my nose to the hairline. I am truly lucky to be alive.
    Mind all the good advice given in this forum about safety. We don't need any more statistics.

  10. #10
    Join Date
    Aug 2006
    Location
    Houma, LA
    Posts
    1,783

    Default

    Darl,


    When we were parked next to you at POG III in Kerrville Martha told me that you had a hard head. This story just proves that she knows you like a book.

    Just kidding; I couldn't resist!

    Thanks for the post: it just may save someone's life!
    Tuga & Karen Gaidry

    2012 Honda Pilot

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