2004 T-800 Air build issues

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Mountain_Dweller, Nov 11, 2019.

  1. Mountain_Dweller

    Mountain_Dweller Bobtail Member

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    Morning,

    Got a 2004 T8 with MXS CAT C-15. When you first start the truck the orange tank takes forever to build, once it hits about 110 psi the green tank shoots up fast, and the orange tank loses pressure pretty fast too. They catch each other at about 90 and build up together until the governor cuts out at 130. Once the governor cuts out the orange tank doesn’t lose air like it did before.

    Thoughts? Thanks!

    -Nathan
     
  2. AModelCat

    AModelCat Road Train Member

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    Leaky 2-way check valve between the primary and secondary tank possibly.

    Air up truck to cutout, shut it off. Open the drain on the primary tank and drain it down to zero. Check gauges. If both read zero, check valve is likely shot. If primary is zero and secondary is still full, build air back up and repeat but drain the secondary tank this time. Secondary gauge should read zero and primary should stay full. If both are empty, likely the check valve.
     
  3. spsauerland

    spsauerland Road Train Member

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    Sounds like normal operation for an ADIS dryer. Snap a picture of your air dryer.
     
  4. Mountain_Dweller

    Mountain_Dweller Bobtail Member

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    Will do. I should have added that the primary air will not build unless you rev the engine, but the secondary builds as normal.

    -N
     
  5. spsauerland

    spsauerland Road Train Member

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    Might want to check hose from compressor all the way to air dryer. They tend to get hard and collapse. I usually disconnect the -10 hose off the compressor and air it up with shop air to isolate between compressor or hose issue.
     
  6. Mountain_Dweller

    Mountain_Dweller Bobtail Member

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    Hello,

    Ok, I tried this test on both tanks and both tanks drained both times. Sure sounds like the check valve, eh?

    -N
     
  7. spsauerland

    spsauerland Road Train Member

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    Is this the air dryer you have?
     

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  8. spsauerland

    spsauerland Road Train Member

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