air pressure problem!

Discussion in 'Questions From New Drivers' started by jmcdaniel05, Oct 6, 2015.

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  1. Oct 6, 2015 #1
    jmcdaniel05

    jmcdaniel05 Bobtail Member

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    New driver here. Just got issued this volvo truck 2012 not aure what model. I have never had to drain air tanks before but Ive been told you are supposed to drain them daily. Well i found three air tanks on left side of cab under battery box. There was only one pull cord on the tank closest to front. Isnt there supposed to be a pull cord for each tank? Anyway problem is I pulled the cord to drain the tanks and now air prwssure is not building up past 100 psi. I pumped brakes to lower pressure till low warning light came on and I was able to build air back up from there but it has stopped at 100 and wont build up farther than that. I dont hear any air leaking out. Oh and after i drained air out of tanks i crawled under to see if petcock valve went back in and it was sticking out. Tried to push it back in but could not. Is there a trick to this?
     
    jmcdaniel05, Oct 6, 2015
    jmcdaniel05, Oct 6, 2015
    #1
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  3. Oct 6, 2015 #2
    jmcdaniel05

    jmcdaniel05 Bobtail Member

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    Got back under truck and valve is not sticking out now
     
    jmcdaniel05, Oct 6, 2015
    jmcdaniel05, Oct 6, 2015
    #2
  4. Oct 6, 2015 #3
    Pmracing

    Pmracing Road Train Member

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    Hopefully more regular use will loosen it up.

    Not sure if a non-gumming lubricant applied conservatively would be advised.

    Mikeeee
     
    Pmracing, Oct 6, 2015
    Pmracing, Oct 6, 2015
    #3
  5. Oct 6, 2015 #4
    STexan

    STexan Road Train Member

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    Regarding the valve you say "won't push back in", I'm not quite sure what you're referring to but if is what I think it is (the cable pull valve??), it won't "push in" while under significant pressure.

    Todays trucks with a working air dryer rarely accumulate any water in the tanks. And it's rare for the dryer to stop drying. I would not worry about. Next time you get to a shop terminal write it up as "missing some air drain cables" and see what happens
     
    STexan, Oct 6, 2015
    STexan, Oct 6, 2015
    #4
  7. Oct 6, 2015 #5
    jmcdaniel05

    jmcdaniel05 Bobtail Member

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    I was actually more concerned about the air not building up past 100 psi. Havent drove truck since i drained the tanks but had it running quite a while for a/c heading out tonight hopefully air will build up more as i drive
     
    jmcdaniel05, Oct 6, 2015
    jmcdaniel05, Oct 6, 2015
    #5
  8. Oct 6, 2015 #6
    STexan

    STexan Road Train Member

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    on some trucks a 100 psi reading might be "normal". Do both tanks read more or less the same? With the wheels chocked and/or engine in gear, tractor and trailer brakes released, and truck engine off and quiet out, can you hear any air leaking anywhere (truck or trailer)?

    As long as you can not hear any air leaking, you should be Ok and the 100 is probably normal.

    Also, does the air dryer "spit" occasionally? A lot? it should not spit every minute or so. If it spits very often and consistently, their is an air system issue.
     
    STexan, Oct 6, 2015
    STexan, Oct 6, 2015
    #6
  9. Oct 6, 2015 #7
    Pmracing

    Pmracing Road Train Member

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    And do your bleed down tests. If it passes no loss test and passes bleed down safety valve tests I think you are good to look for more other problems! hahahaa #usedtrucks

    Mikeeee
     
    Pmracing, Oct 6, 2015
    Pmracing, Oct 6, 2015
    #7
  10. Oct 6, 2015 #8
    77fib77

    77fib77 Road Train Member

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    Turn off the truck, do you hear air leaks???
     
    77fib77, Oct 6, 2015
    77fib77, Oct 6, 2015
    #8
  11. Oct 6, 2015 #9
    jmcdaniel05

    jmcdaniel05 Bobtail Member

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    No air leaks and both tanks are at same pressure and i did pump brakes til low warning light came on and it built back up to 100 and stayed there
     
    jmcdaniel05, Oct 6, 2015
    jmcdaniel05, Oct 6, 2015
    #9
  12. Oct 6, 2015 #10
    AModelCat

    AModelCat Road Train Member

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    My question is did it build above 100 psi before you drained the tanks? 100 psi seems a bit low but it could be within spec still. Usually its just an adjustment on the governor. A mechanic can adjust that in 5 minutes if needed.
     
    AModelCat, Oct 6, 2015
    AModelCat, Oct 6, 2015
    #10
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