Secondary air fills before primary

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Bigjoe78, Jun 16, 2017.

  1. Bigjoe78

    Bigjoe78 Bobtail Member

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    Oct 3, 2016
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    Hello
    I have a 2007 Century with a 60 Detroit. The other day I turned the truck on and it started purging air from the dryer about every five seconds. I jad been hearing the dryer "rattle snake" for a while so I decided to pull it off and check ot out. I am no way a mechanic but a lil handy wuth tools. After speaking with parts guy i bought the govenor, purge valve and filter cartridge. Replaced them since it was cheaper than a new dryer. As soon as I turned the truck on with the new parts, it purged 3 times and then my 2ndary tank started to fill before my primary. I turned ofd the teuck and bled the air down to zero. Turned the truck back on and the primary filled first as normal without any purging from the dryer. I took a load and about 130 miles in my abs main valve started leaking from the bottom. I replaced it and it still leaked. After checking all brake chambers as I read on another thread it still leaked. Found it to be the other valve I believe it is tbe quick release valve had a little hole in a seal inside. I replaced that valve, no more leaks but it still purges 3 times at start up and fills my secondary tank before my primary. This is the whole reason I replaced the parts and the dryer to begin with. Can anyone help me. Thanks for your time.
     
  2. Strange77

    Strange77 Light Load Member

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    So in your post at one point you said you didn't replace the dryer and at the end you said you replaced the dryer. Did you replace it or not?
     
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  3. Bigjoe78

    Bigjoe78 Bobtail Member

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    Not the complete dryer. Only the purge valve, govenor, and filter cartridge.
     
  4. Strange77

    Strange77 Light Load Member

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    Ok cause I have noticed on the air dryers I've replaced recently (I do very few) but after replacing dryer I find that the 2nd tank fills before the primary and it threw me for a loop as well to the point I've double and triple check my primary line was connected to the primary port and the secondary line was connected to the secondary port. The only thing I can think of is that possibly they've been re-engineered to fill that way and (just me tossing ideas out there) the thought behind it was to keep drivers from filling primary and taking off or possibly if you happen to spring a bad leak on the primary side, secondary would begin to fill primary to give you a little longer to get off the road possibly in an all out failure situation like the air compressor failed too or couldn't keep up. But that was really just me trying to understand why they all seem to do that know after I replace them. They come it filling primary to secondary and they leave filling secondary to primary.
     
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  5. Bigjoe78

    Bigjoe78 Bobtail Member

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    So I guess I shouldn't worry as long as I'm building air at a proper rate and it's holding? It's just something I have to get used to I guess. I appreciate your time and help.
     
  6. driverdriver

    driverdriver Road Train Member

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    My 16 did that and now my 18 crapcadia does it as well. Primary first then secondary.
    Only answer I've ever been able to get out of freightliner is ' because it's your primary first secondary second,' yep seriously.
     
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  7. Bigjoe78

    Bigjoe78 Bobtail Member

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    On mine its my secondary first, then my primary.
     
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  8. E model Cat man

    E model Cat man Light Load Member

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    Their is a wet system that feed both the primary and secondary systems with double check valve between primary and secondary or just a regular check valve. Probably has a sticky check valve thats causing the secondary to fill first.
     
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  9. Bigjoe78

    Bigjoe78 Bobtail Member

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    I'll look into that thanks.
     
    E model Cat man Thanks this.
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