Air dryer safety valve popping off when cold

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by SemperFiServices, Nov 13, 2019.

  1. SemperFiServices

    SemperFiServices Medium Load Member

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    Indianapolis, IN
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    Hey y'all, I've researched as much as I could and I'm still lost. I have a Bendix AD-IS in this Pro Star I just bought- still working out the bugs Knight didn't. O bought the truck a couple months ago when it was warm. First time it dropped into the low 40's, the air pressure would build to about 140 psi or so on the gauges, and the safety valve would pop, air pressure would drop to about 70 psi, and build back up.

    Last night, I hunkered down under 2 comforters and shut her down as it hit 16° in upstate NY. I started the truck this morning, and it must've popped off about a good 8-10 times until it finally warmed up enough and purged at 120 psi like it's supposed to.

    Any idea why the cold is causing the air drier to build up too much pressure?
     
  2. tommygun58

    tommygun58 Light Load Member

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    Sep 22, 2015
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    Gov. May be bad? Just a guess
     
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  3. Cat sdp

    Cat sdp . .

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    Orion's Belt
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    Cartridge is probably full of crap and heat for the air drier isn’t working...
     
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  4. Goodysnap

    Goodysnap Road Train Member

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    I would say your dryer was never serviced, the desiccant is oversaturated and you have moisture floating in the system. Drain the tanks thoroughly while above freezing. Replace the dryer complete with new, and keep the filter changed annually or more often for extreme service.
     
  5. jed222

    jed222 Bobtail Member

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    Nov 14, 2019
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    Sounds like the filter is saturated service the dryer check the complete reman pricing sometime they aren’t much more that a filter and purge kit then it’s just r&r
     
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  6. SemperFiServices

    SemperFiServices Medium Load Member

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    Jan 29, 2013
    Indianapolis, IN
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    Thanks everyone for the responses. I think I might just replace the whole thing with an aftermarket unit from Ebay or Amazon for under $150. After 500,000 miles it couldn't hurt.
     
  7. Goodysnap

    Goodysnap Road Train Member

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    I would be leery of any new dryer bought on Amazon or EBay for that price. You may be buying a expensive boat anchor. I would shop around and find the best deal on a new bendix at a local parts house you know.
     
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  8. Final Drive

    Final Drive Medium Load Member

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    Op
    When all is said and done, learn how to bypass your dryer. I had to bypass mine at 17 below..
     
  9. Rideandrepair

    Rideandrepair Road Train Member

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    Truckpro has Armada AD9 $190
     
    Last edited: Dec 2, 2019 at 10:14 PM
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