2002 Volvo VNL 780 Air PSI Issue

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by JRK, Aug 1, 2021.

  1. JRK

    JRK Bobtail Member

    7
    0
    Feb 18, 2016
    0
    picked up truck after having it serviced a
    2002 Volvo VNL 780
    VIN 4V4NC9TJ12N331024
    Engine serial ISX 475HP 14020915
    shop is closed had to drive home with this, there is 115 psi in air tanks , breaks release, air to suspension.
    No Air to Splitter or Cab air bags or to raise or lower suspension or engage rear differential.
    any help would be appreciated.
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

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

  3. AModelCat

    AModelCat Road Train Member

    27,626
    144,548
    Jul 7, 2015
    Canuckistan
    0
    Sounds like the pressure protection valve is sticking. Probably located on one of the air tanks.
     
    spsauerland Thanks this.
  4. Team818

    Team818 Medium Load Member

    397
    626
    May 5, 2019
    0
    I hope he can correct that. Wow. The mechanical forces released that Truck to soon. My goodness I hope its doesn't cause a incident on the highway. Might want to U Turn and get back there asap, what if the brakes all apply at the same time..... yikes.
     
  5. JRK

    JRK Bobtail Member

    7
    0
    Feb 18, 2016
    0
    i have never heard of that what does it look like
     
  6. AModelCat

    AModelCat Road Train Member

    27,626
    144,548
    Jul 7, 2015
    Canuckistan
    0
    Purpose of the pressure protection valve is to protect air supply for the brakes. All it is is a valve that won't let air flow from the tanks to the air operated accessories until a specific system pressure is reached. Ever notice how once a truck hits about 90 PSI the cab and suspension inflate? That's the pressure protection valve opening.
     
    spsauerland and Goodysnap Thank this.
  7. JRK

    JRK Bobtail Member

    7
    0
    Feb 18, 2016
    0
    i didnt know till i was on the way home , no place to turn around. made it home safe and put truck in the air i thought tech may have disconnected or some thing came lose by accident.
     
  8. AModelCat

    AModelCat Road Train Member

    27,626
    144,548
    Jul 7, 2015
    Canuckistan
    0
    Google search " Bendix pressure protection valve" there's a few variations that look different.
     
  9. JRK

    JRK Bobtail Member

    7
    0
    Feb 18, 2016
    0
    i have heard of tractor protection valve, i had air to brakes and all air bags just not cab bags suspension and splitter, it is a 13 speed
     
  10. Team818

    Team818 Medium Load Member

    397
    626
    May 5, 2019
    0
    Oh thank the Lord. It made it to your place.
     
  11. JRK

    JRK Bobtail Member

    7
    0
    Feb 18, 2016
    0
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

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