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ABS modulator Valve leak

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Wvpete2019, Dec 13, 2019.

  1. Dec 13, 2019 #1
    Wvpete2019

    Wvpete2019 Bobtail Member

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    Dec 13, 2019
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    Have a 2001 Pete 379 that the passenger side modulator valve leaks when realeasing the parking brake. When it leaks maxi brakes will not release. Doesn’t do it all the time seems to be an intermittent problem. But if you apply the brake pedal when it’s leaking it’ll stop and brakes will release. I’ve checked maxis don’t seem to be an issue. Anyone have any ideas?
     
    Wvpete2019, Dec 13, 2019
    Wvpete2019, Dec 13, 2019
    #1
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  3. Dec 14, 2019 #2
    Raffito

    Raffito Light Load Member

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    Aug 25, 2019
    Ingram, TX
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    Looks like you have a leaking brake chamber. You can check that by removing the service brake hose and see if air is coming out when you release the parking brake. An other easy way is to cover the exhaust port on the modulator valve and is the rod on the chamber start moving out you know you have a bad chamber.
     
    Raffito, Dec 14, 2019
    Raffito, Dec 14, 2019
    #2
    spsauerland and Heavyd Thank this.
  4. Dec 14, 2019 #3
    Heavyd

    Heavyd Road Train Member

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    Center seal on brake chamber will cause this. Park brake air will leak through the middle of the chamber and out the service side to the exhaust of the abs modulator.
     
    Heavyd, Dec 14, 2019
    Heavyd, Dec 14, 2019
    #3
    spsauerland Thanks this.
  5. Dec 15, 2019 #4
    spsauerland

    spsauerland Road Train Member

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    May 31, 2010
    West Harrison, In
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    Was another guy posted awhile on a Sunday with same issue. His ended up being the QR-1C that controls the parking brakes.
     
    spsauerland, Dec 15, 2019
    spsauerland, Dec 15, 2019
    #4
  7. Dec 15, 2019 #5
    Wvpete2019

    Wvpete2019 Bobtail Member

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    Dec 13, 2019
    0
    Thanks everyone for the responses. I had already tried taking the service lines of the chambers and none of them leaked threw. Still puzzling to me because yesterday the truck worked flawless. I’m thinking there was a chance of a little ice build up. But I will keep all the responses in mind if it occurs again. Had someone else mention the QR valve so maybe give it a shot.
     
    Wvpete2019, Dec 15, 2019
    Wvpete2019, Dec 15, 2019
    #5
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