Air pressure in secondary line won't go up to normal level

Discussion in 'Freightliner Forum' started by expedite_it, Sep 13, 2024.

  1. expedite_it

    expedite_it Road Train Member

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    When I was driving to the truckstop, I thought that maybe the air compressor on the truck is defective. But now I don't think that the air compressor is defective. If the air compressor was defective, I don't think the primary air line would have 120 psi with the engine turned off.

    I think you are right that there is a leak of some kind.
     
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  3. expedite_it

    expedite_it Road Train Member

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    @Rideandrepair
    @Ridgeline
    Does anyone have any idea as to why the air pressure in both the primary and secondary air lines rose almost to normal pressures when I idled the truck engine for about two or three minutes to microwave food last night?

    The mechanics have not worked on the truck yet. I don't get it. I am baffled.
     
    Last edited: Sep 14, 2024
  4. Ridgeline

    Ridgeline Road Train Member

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    It is obvious … you have an air leak, maybe simple to find.
    upload_2024-9-14_7-43-17.jpeg
     
  5. expedite_it

    expedite_it Road Train Member

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    About 4 days ago, I accidentally drove my semi-truck all day with the air bags dumped. Do you think that my driving with the air bags dumped all day could have caused the leak?

    @Ridgeline
    @Rideandrepair
     
    Last edited: Sep 14, 2024
  6. expedite_it

    expedite_it Road Train Member

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    The photograph above is a photograph that I took of my truck about an hour ago. The air pressure in the secondary dropped overnight to 25 psi.

    I found the photograph below this sentence on my cell phone. The photograph below is a photograph of a different Freightliner truck than the Freightliner truck I have now. On this Freightliner truck four years ago, both the primary and the secondary air pressures were at about 120 psi with the engine off. I think that is how my current truck would normally be with the engine off.
    ---------------
    So the two photographs on this post are photographs of two different trucks, but both of the trucks are Freightliner Cascadias.
     
    Last edited: Sep 14, 2024
  7. SmallPackage

    SmallPackage Road Train Member

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    Yes. If an air spring was damaged and has a slow leak it will bring the secondary side down. Pretty good in 10 years you’ e only done that once. Lol.
     
    Rideandrepair Thanks this.
  8. North Pole Nightmare

    North Pole Nightmare Heavy Load Member

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    Dump your suspension switch if you have one,if the pressure goes back to normal then your suspension has a leak.If you don't have the dump switch you can chock the wheels ,release the brakes,and look for the leak.
     
    expedite_it Thanks this.
  9. expedite_it

    expedite_it Road Train Member

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    I do have a suspension switch.

    I'm assuming "dump your suspension switch" means dump the air bags. I suppose I should perform that test with the truck parked and the engine idling; correct?
     
  10. North Pole Nightmare

    North Pole Nightmare Heavy Load Member

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    Yes
     
    expedite_it Thanks this.
  11. expedite_it

    expedite_it Road Train Member

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    If the pressure does not go back to normal when i dump my air bags, what does that indicate? Where would my leak be then?
     
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