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How do I find an air leak ?

Discussion in 'Truck Talk' started by ChanceMaster, Aug 29, 2012.

  1. ChanceMaster

    ChanceMaster New Recruit

    I am losing pressure from my secondary tank after sitting overnight . Seems to go down to around 50 psi. Sometimes the primary tank loses pressure as well, but not everytime. I wonder what the best way to discover the source of the air leak ? Any tips or suggestions for this mechanically inept driver would be appreciated.

    Also : During normal operation, the air pressure is as it should be. I cannot hear any obvious leaks.

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    Last edited: Aug 29, 2012
  2. The Enemy

    The Enemy New Recruit

    O.e thing you can do is get a spray bottle with soapy water and start spraying at your secondary tank, then the lines and go from there. Look for bubbles after you spray and you might find your air leak.
  3. ChanceMaster

    ChanceMaster New Recruit

    That might work, ill try it. Thanks.

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  4. Deville

    Deville Rookie Expediter

    Pin hole air leaks are like trying to find needles in a hay stack. The Enemy's way is most likely the best way. You may get lucky & hear it if you're ears are in tune.
  5. ChanceMaster

    ChanceMaster New Recruit

    My ears are in tune to any noise that affects the truck owners bank account or my potential to earn.

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  6. Mdbtyhtr

    Mdbtyhtr Rookie Expediter

    I used freon at the air compressor out port and quickly tightened it back up and used my freon leak detector to find the leaks. I even found a screw into the air line leading to the roof mounted air horns that was behind interior trim, it was one you could never hear. The soapy water in a spray bottle works for the more obvious leaks. Spray all connections, exhaust ports on brake valves and any where air lines are retained by clamps.

    Last edited: Aug 30, 2012
  7. ChanceMaster

    ChanceMaster New Recruit

    More good advice . I hope its not happening in an interior / inaccessible place.

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  8. The Enemy

    The Enemy New Recruit

    Few other things i forgot to mention. Look for spots of chaffing along your air lines,, second, check your air tanks for any exterior rust or corrosion. It might be a tiny pinhole letting air slowly escape the tank..
  9. jjoerger

    jjoerger Seasoned Expediter

    We found a leak on the fitting on the back of our air gauge. Heard it when I pulled the dash out to change a light bulb. Also found a pin hole on an air bag. Slow leaks are really hard to find. Soapy water works well.
  10. ChanceMaster

    ChanceMaster New Recruit

    Ok...didn't even think of the air bags..thanks ! Just left the truck for about 3 hours...secondary was below 50 psi. More than a pinhole I'm thinking .

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  11. ChanceMaster

    ChanceMaster New Recruit

    My NEXT question is : will the parking brake still hold if pressure drops in both air tanks during the night while sleeping ? I'm a little concerned. ( straight truck ) .

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  12. BigCat

    BigCat New Recruit

    Yes if the pressure drops the brake will hold. That's the reason the knob pops out if it gets below 40-60 psi.
  13. zorry

    zorry Active Expediter

    Chance,since you asked that question, if you drop below 60 lbs or so there are large springs in your parking brakes that will lock up your brakes.
    If you're moving and have sudden large air lose,you'll be stopping,wether you want to or not. Get to the shoulder quickly.
    You'll be stopped until you can regain air pressure.
    You can bypass the spring brakes ( called caging the springbrake ) but once you release them, if you have little air you'll have zero brakes.
    Zero brakes are only fun until you have to stop.
  14. BigCat

    BigCat New Recruit

    Yea definitely don't want to drive with caged brakes. Lol We did that when I did decked tractor loads just incase one had a slow leak. You don't want the air to leak and lock brakes up with a 4 way load.
  15. ChanceMaster

    ChanceMaster New Recruit

    I thought I remembered the mention of spring brakes from driving school, but thought perhaps that was exclusive to trailer brakes. Good info everyone, thanks for all the advice. I don't know much about mechanics but really trying to learn what I need to know to keep rolling.

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  16. BigCat

    BigCat New Recruit

    Like sorry said just keep an eye on your air gauge and pull over if it gets abnormally low. As for the leak check around fittings first. The push in fittings typically will twist letting air escape. If those are good check around the bottom of truck.

    Another thing is if you drain the water from tanks check the petcock valve and see if it is slightly wedged. If there is rust in the tank it could wedge just enough to let it leak.
  17. ChanceMaster

    ChanceMaster New Recruit

    More good info from people
    Who know...thanks, going to start in a.m. by buying some dish detergent and making some soapy water to spray around. Truck next to me is idling so ill wait till they leave so I cam hear.
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  18. BobWolf

    BobWolf Active Expediter

    60 pounds over nite is allot!
    Annother tool is old stethescope or a peice of tubing plastic or hard rubber abbout a foot or two in length place one end to your ear and run allong the brake lines if somthing is leaking you will hear it. Both work the same just remember the sound will be amplified It helps to cover your other ear if there is noise arround you or when you start to zero in on the leak.
    You can buy a basic student stethescope should run ten or fifteen bucks. Lots of other uses too arround the truck finding noises. Body, chasis, and engine noises, draping it over your neck to impress the girls at the bar, checking bearings, tracking down air leaks. .

    Bob Wolf
    Last edited: Aug 30, 2012
  19. bluejaybee

    bluejaybee New Recruit

    If I don't park my truck pretty level, it will bleed the secondary down through the load leveler valve on my air bags. And it is sometimes 50 or 60 lbs overnight. This is normal.
  20. zorry

    zorry Active Expediter

    Moving around in the truck,climbing in and out will cause lose in air bag usesge.
    Next time you will be out of the truck for an extended period,check the pressure drop.

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