Strange air leak

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Freightlinerbob, Dec 9, 2015.

  1. Freightlinerbob

    Freightlinerbob Road Train Member

    2,234
    1,315
    Jan 15, 2012
    West Coast B.C.
    0
    The leak is on the "B" reservoir. Here are the symptoms:
    -Driving down the road the compressor cycles every few minutes.
    - When parked with parking brakes applied, it leaks just as fast.
    - When parked with parking brakes released, the leak seems to stop, more or less. (30 minutes to leak from 120 to 100 psi. )

    I've sprayed down everything I can think of with soapy water and can't find anything.

    Any ideas?
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. mountaingote

    mountaingote Road Train Member

    2,026
    7,916
    Sep 22, 2012
    0
    Sounds like a valve problem
     
  4. Freightlinerbob

    Freightlinerbob Road Train Member

    2,234
    1,315
    Jan 15, 2012
    West Coast B.C.
    0
  5. AModelCat

    AModelCat Road Train Member

    27,627
    144,557
    Jul 7, 2015
    Canuckistan
    0
    Is B the primary or secondary reservoir?

    Have you checked the exhaust ports for leakage at every valve you can find? I would guess that maybe you have a valve that's leaking. Possibly a check valve in the air system sticking, which would cause you to only draw air from the B tank rather than blended air from both for the trailer supply or air accessories such as suspension.
     
  6. baha

    baha Road Train Member

    4,137
    2,832
    Jul 25, 2013
    ga
    0
    CK. your firewall for air leaks from dash valve ex. line plastic line that is ending outside firewall so you will not hear air release from air brake valve inside dash so any leaks can be heard at eng. side of firewall, also ck. foot valve ex. port for leak?
     
    Last edited: Dec 9, 2015
  7. Freightlinerbob

    Freightlinerbob Road Train Member

    2,234
    1,315
    Jan 15, 2012
    West Coast B.C.
    0
    Yea the B tank is the secondary tank.

    I should mention that when parked with parking brakes released and the suspension relaxed the air is not leaking. It doesn't matter if the engine is running or off, it does not leak. This is just as if the truck was driving except that it isn't moving. Yet when it is moving, it leaks.
    Now I just parked it without applying parking brakes and let it settle for 10 minutes, then applied the parking brakes. The air leak is significantly reduced. Although it still leaks somewhat.
    I'm thinking its in the air suspension.
     
  8. Ozdriver

    Ozdriver Heavy Load Member

    767
    1,390
    Oct 16, 2015
    Australia
    0
    It can be hard finding an air leak in an airbag especially when there's no weight on it. I've had to isolate each airbag in turn before I found a leak. I would first be isolating the whole suspension system from it's air supply as a first off. You'll need some 1/4" or 3/8" blanking plugs for this.
     
    AModelCat Thanks this.
  9. swaan

    swaan Road Train Member

    2,943
    4,371
    Jul 12, 2009
    BC canada
    0
    Could be bad leveling valve .
    Park it and dump the air in suspention.
    Air ride cab??
    Could be leveling valve on there too.
     
  10. Freightlinerbob

    Freightlinerbob Road Train Member

    2,234
    1,315
    Jan 15, 2012
    West Coast B.C.
    0
    Cab air bags and valve are new. I've double checked them as well. Parked with air suspension dumped. This made no difference, so I'm back to thinking its not the suspension.
     
  11. Ozdriver

    Ozdriver Heavy Load Member

    767
    1,390
    Oct 16, 2015
    Australia
    0
    It isn't unheard of for the air from the primary tank to bleed back into the compressor. You could disconnect the line from the compressor port and see.
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.