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foot valve exhausts mid stroke

Discussion in 'Trucks [ Eighteen Wheelers ]' started by chris316, Sep 25, 2011.

  1. Sep 25, 2011 #1
    chris316

    chris316 Bobtail Member

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    Sep 25, 2011
    noname, oklahoma
    0
    I have a 2001 International 4700 that leaks air at foot valve exhaust only when pedal is pressed about half way. I have replaced foot valve and isolated leak to secondary system and dont know what valve to go after next. I have also made sure all lines at foot valve were hooked up right. Parts are too expensive to just try one after another and I dont have any service manuals to go off of. Any ideas would be appreciated
     
    chris316, Sep 25, 2011
    chris316, Sep 25, 2011
    #1
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  3. Sep 25, 2011 #2
    JohnP3

    JohnP3 Road Train Member

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    Feb 21, 2010
    Rock Creek B.C. Canada
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    You are sure you are not hearing the exhaust hose from the hand valve, there should be no exhaust coming from the foot valve if the pedal is held steady, try using a bar to hold it down at 50 lbs, then at 100. Once the system stabilizes the pressure should hold steady.
    If a highway valve, two way check valve, it may allow air to exhaust from the foot valve if the hand valve is applied, or from the hand valve if the foot valve is applied.
     
    JohnP3, Sep 25, 2011
    JohnP3, Sep 25, 2011
    #2
    chris316 Thanks this.
  4. Sep 25, 2011 #3
    Prairie Boy

    Prairie Boy Road Train Member

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    Edmonton, AB
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    Change it!! Just changed one 3 weeks ago that was doing the same thing. Haven't had a problem since. It didn't do it every time but I would say 75% of the time. If I pushed it harder to increase the pressure it would sometimes stop exhausting.
     
    Prairie Boy, Sep 25, 2011
    Prairie Boy, Sep 25, 2011
    #3
    chris316 Thanks this.
  5. Sep 25, 2011 #4
    chris316

    chris316 Bobtail Member

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    Sep 25, 2011
    noname, oklahoma
    0
    Definitely leaks at foot valve exhaust port with steady pressure on pedal. Thought maybe I got a bad one so I got another one and still have the same thing. Only leaks at mid travel, if I let it build to operating pressure shut down and drain secondary tank it doesn't leak. This truck does not have a hand valve, only parking brake valve. Need to know what other valve/valves could leak back to foot valve.
     
    chris316, Sep 25, 2011
    chris316, Sep 25, 2011
    #4
  7. Sep 25, 2011 #5
    Heavyd

    Heavyd Road Train Member

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    If you are sure it is the foot brake valve leaking out the exhaust constantly, the only valve connected to the secondary system and secondary brake system is the Inversion valve. It may be possible that valve is leaking back through the secondary brake lines when the brakes are applied. The pressure is getting built up, over coming the balance spring and lifting the exhaust valve off it's seat.
     
    Heavyd, Sep 25, 2011
    Heavyd, Sep 25, 2011
    #5
    chris316 Thanks this.
  8. Sep 28, 2011 #6
    chris316

    chris316 Bobtail Member

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    Sep 25, 2011
    noname, oklahoma
    0
    I wish I had a service manual as I'm not sure if this truck has all the valves I've seen in air brake troubleshooting books i have access to. In the process of looking for inversion valve i have found at least two dc-4 double check valves. I checked both with shop air and they seem to work correctly however when I leave one supply line off of one of them leak at pedal is gone. Dont know if that helps me narrow down anything though. There is a valve attached to bottom of antilock module that delivery from dc-4 feeds. Have not found any that resemble inversion valves i've seen. There is a valve on frame ahead of rear axle but numbers off of it don't seem to come up when I search online. I can post pictures of it and other valves if that might help.
     
    chris316, Sep 28, 2011
    chris316, Sep 28, 2011
    #6
  9. Sep 28, 2011 #7
    Heavyd

    Heavyd Road Train Member

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    That other valve is probably a Spring brake modulating valve, or an R-7 valve. Kinda the same as the Inversion valve.
     

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    Heavyd, Sep 28, 2011
    Heavyd, Sep 28, 2011
    #7
    chris316 Thanks this.
  10. Sep 29, 2011 #8
    chris316

    chris316 Bobtail Member

    5
    0
    Sep 25, 2011
    noname, oklahoma
    0
    Thank you all for the help. Today I pulled the valve previously mentioned apart and found O'rings swelled and two rolled in bore. I believe this is due to compressor failure awhile back. After replacing compressor I replaced complete dryer assembly but evidently more oil got in system than I had thought. Stll not back to normal but between new foot valve and resealing ?inversion? valve it is alot better. Now on to multiple oil leaks at DT466E. Thanks again.
     
    chris316, Sep 29, 2011
    chris316, Sep 29, 2011
    #8
  11. Sep 29, 2011 #9
    Heavyd

    Heavyd Road Train Member

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    That can be a real bugger!
     
    Heavyd, Sep 29, 2011
    Heavyd, Sep 29, 2011
    #9
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