help with air system

Discussion in 'Trucks [ Eighteen Wheelers ]' started by gunner76, Aug 3, 2011.

  1. gunner76

    gunner76 Medium Load Member

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    I'm having some issues with the air system in my new truck. When I was on the 400 mile trip home from the dealer it started acting up. Evertime the air compressor would need to kick in the airdryer would spit really fast for 1-2min then stop and allow the compressor to fill the tanks. When I got home I checked the airdryer and it was still the original(truck is 4yrs old), so I replaced the dryer and also replaced the govenor since it was a cheap and easy repair. These repairs helped alot, but I'm still getting a fast spitting sound when the compressor kicks in, but now it only lasts for a couple of seconds and it only does it when the RPM's are above slow idle. At slow idle it usually just spits once and then fills the tanks.I checked for any air leaks in the lines going from the dryer to the govenor and compressor and found none. My mechanic says it could be the unloader valve that is on the top of the compressor since everything else has been replaced. Could this be the problem or could the new air dryer possibly be bad?
    Once the spitting stops the system works normally and the dryer pops like it should when the tanks are full.
     
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  3. Pablo-UA

    Pablo-UA Road Train Member

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    check for water, emulsion in tanks, try to dump some air

    try to rebuild air drier unit with genue parts.
     
  4. JohnP3

    JohnP3 Road Train Member

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    The unloaders are definitely a good possibility as your problem if they are leaking past the seals the air pressure when the compressor unloads.
    The unloaders work when the system gets to the governor set pressure, if they are leaking the air will leak into the intake air and the compressor will cycle. Usually every 15 seconds or so.
     
  5. Pablo-UA

    Pablo-UA Road Train Member

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    as I can see when drier filter was not changed in time a lot of crap may be inside air system, so unloaders, four way valve, air drier unit may be damaged with emulsion
     
  6. Heavyd

    Heavyd Road Train Member

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    Unloaders in compressor.
     
  7. Pablo-UA

    Pablo-UA Road Train Member

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    ouh yeah! :biggrin_25525:
     
  8. Superhauler

    Superhauler TEACHER OF MEN

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    ditto on the unloader valve easy fix.
     
  9. gunner76

    gunner76 Medium Load Member

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    I went ahead and put new a new unloader valve in the compressor, it didn't make a difference. I also got the dealler to warranty the purge valve in the airdryer and changed that but it didn't make a difference either. I then tried a whole new line from the govenor to the dryer to see if maybe there was a small leak somewhere I missed but the line made no difference. I then even tried a different govenor and didn't get any different results.
    I had a guy tell me that maybe the check valve on the dryer thats ahead of the line going to the tank might be bad so I might see if I can get the dealer to warranty that.
    There didn't seem to be any noticable water in the tanks the couple of times I drained them. I don't know what else to check, and the mechanic seemed puzzled by the noise too. I thought maybe the spitting for a couple of seconds at the beginning of the compressor cycle was normal for this setup, but the mechanic said it shouldn't do it.
     
  10. Heavyd

    Heavyd Road Train Member

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    Did you replace the who the drier with a reman unit or just the cartridge? Some driers have a "turbo cut off valve" inside them that may be sticking. What kind of drier and engine do you have?
     
  11. Kittyfoot

    Kittyfoot Crusty Ancient

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    BbbbbTW, It's nnnnnot "spitting", it's ssssssssssssstuttering an it nnnnnnnnnot nnnnnice to mmmmmmmmmmmake ffffffffffun of it.:biggrin_25513:
     
    T-RIX Thanks this.
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