Air Leak from Truck Height Control Leveling Valve Normal?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by PE_T, Jul 5, 2019.

  1. PE_T

    PE_T Road Train Member

    So we all get some air leak through it when we’re getting loaded or unloaded, but how much air leak is too much? I sometimes have to air up my tanks right after loading/unloading. Should I be worried? I don’t remember the last time the height control leveling valve was replaced. This is on a 2014 Freightliner Cascadia DD15.
     
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  3. skellr

    skellr Road Train Member

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    Sounds normal to me. It's always purging air when getting loaded or fighting to supply air are when you are getting unloaded. I don't think they are required to compensate for such drastic changes.

    Wait until after the job is done and then do an "air test" to see if it's acceptable.
     
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  4. flood

    flood Road Train Member

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    Leaking when being loaded/unloaded it normal..
     
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  5. Goodysnap

    Goodysnap Road Train Member

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    Depends on where its leaking from? Break out the soapy water. Wiggle the lever and watch for leaks where the shaft enters the valve and all the fitting and air line joints. The only place leaking should be present is from the exhaust port during leveling out, as allready mentioned which is completely normal.
     
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  6. rcelmo

    rcelmo Medium Load Member

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    When you do your "leak down test" during your pretrip how
    much air pressure do you lose?
     
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  7. PE_T

    PE_T Road Train Member

    I must admit I haven’t done it for months now, but my air leaks overall are mostly under control as I fix them all myself. I usually just wait until my air tanks are continuously under 75 PSI after a 10-hr break (both breaks set) or under 75 PSI after 30 min to a few hours (trailer breaks released). I am aware this isn’t the official test.
     
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  8. rcelmo

    rcelmo Medium Load Member

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    Sounds like everything is fine. Since the leveling valve is connected
    to the air bags "obviously" it is normal to hear air leaking during loading
    and unloading. As long as the truck isn't leaking a significant amount of
    air I would not worry to much about the leveling valve.
     
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  9. boneebone

    boneebone Road Train Member

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    If it’s not leaking otherwise, except for loading and unloading, than it’s normal.
     
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  10. Rideandrepair

    Rideandrepair Road Train Member

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    The problem I’ve had, is an old valve will tend to stick and seep, sometimes intermittently, taking a long time to settle. I had a DOT ask once, “ What’s that leak, leveling valve?
     
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