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Thread: Air leak

  1. #1
    Junior Member
    Join Date
    Sep 2014
    Dingmans ferry pa

    Air leak

    2001 classic. Air seeping from the foot valve exhaust, also air dryer valve wont stop purging until I hit the brake hard or pressure reaches 110 psi. assuming air dryer is doing this because the foot valve is leaking air. replaced foot valve twice, replace entire air dryer, unloaders, governor and cab valve. Foot valve leeks air running or not and with or without trailer. any suggestions.

  2. #2
    OK- For starters your going to be looking at two separate issues here -

    On the air dryer- Depending on what dyer model you have it can be normal for some to have extended drain after purge but it should stop leaking after a certain amount of time at about the same time interval. Assuming the governor is either remote mounted , or mounted directly to the compressor- I would begin by checking the reservoir and unloader (Small lines 1/4") lines for leaks. If you have leaks in these areas you will have delayed and or improper dryer purge operation. Your cutout should be between 120-130psi , not 110. compressor should come on around-90 purge 120-130.

    On the treddle valve issue- I would begin by isolating all of your drive axle park brake chambers and check for bleed through to the service side with the emergency brakes released. Disconnect all the service lines from the spring brakes one at a time to see if you find one of them back-feeding. If you find nothing there then remove the lines from the foot valve one at a time until you find the source of the leak. Trace back to see where it's coming from. (this may prove difficult without a plumbing schematic)It is highly unlikely that the valve itself is the issue.



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