Question about tractor protection valves

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by JamesMc84, Jul 27, 2021.

  1. JamesMc84

    JamesMc84 Bobtail Member

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    Mar 20, 2017
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    Is the service side suppose to have a tractor protection valve ? Or just the supply/emergency side?

    I’ve always tested tractor protection valves by depressing the supply dash valve and waiting for the tractor protection valve to cut off air.

    but I’m reading something that is saying there is one on the service side as well?

    can anyone confirm?


    I’m plumbing this international to tow air brake trailers and I believe I got the supply side all figured out. Just need to figure out the service side now
     
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  3. skallagrime

    skallagrime Road Train Member

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    Apr 10, 2012
    Indiana
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    No service side valve, when the trailer park brake (supply) is released air flows on pedal to service, when trailer park brake is set, there is no flow to service line on trailer
     
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  4. MLC Adventures

    MLC Adventures Medium Load Member

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    May 2, 2021
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    You will need a quick release valve on the service line to trailer though.
     
  5. baha

    baha Road Train Member

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    Jul 25, 2013
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    When the red valve is pulled out and when your foot is on brake no air should be able to flow out of blue line end where it hooks on to trailer, if any air comes out your OOS.there was a DOT cop on the W. bound side of I-40 just past the bridge that's out down for repairs, that would ck. for that leak and the part from truck dealer was close to 200$$, I caught a ride from a ser. truck across the river that was fixing several trucks for that part, we went to several dealers and got the part for big co. trucks and truck parts places where I got for 40 bucks that fit my truck and had it put on, and DOT man ck. it and signed my oos order so I could leave out after Paid my oos. fine??
     
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