Peterbilt suspension dump problem

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by TortuousAugur, Oct 25, 2021.

  1. TortuousAugur

    TortuousAugur Bobtail Member

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    Sep 3, 2013
    Dallas, TX
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    I'm having an issue where the truck's dump port on the right height leveler valve is being supplied with just enough air to engage the suspension dump and is also causing air to come out of what I'm guessing is the overfill protection valve (a rubber flap coveringa square hole). This air stops if I turn on the dump switch in the cab and turn it off but it starts back up within a few minutes.

    Does this indicate a bad governor or does anyone know where I can find a guide to diagnose what the issue is?
     
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  3. Goodysnap

    Goodysnap Road Train Member

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    Year, model and VIN.

    Are you saying with the suspension dump switch off there is still air signal at the leveling valve dump line?
     
  4. TortuousAugur

    TortuousAugur Bobtail Member

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    Sep 3, 2013
    Dallas, TX
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    2016 Peterbilt 579 last 8 GD587522.

    Yes, you are correct. Switch is off but it will still supply air to the dump valve on the leveler. It stops for a few minutes if I turn the dump switch on and back off again.
     
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  5. Goodysnap

    Goodysnap Road Train Member

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    Under the cab or between the framerails you will find a bank Electric over air actuator solenoids for air controls. There will be atleast 2 or 3 the same with one odd one that looks like 2 together and slightly different. This odd one is your susp. Dump. Air line on the EOA should color match the signal line at the level valve.
    Tap the EOA with screwdriver handle and see if it reacts or shuts off. Dead giveaway and most likely cause is stuck valve.

    Next stop is supect wiring issue on chassis harness, inspect under cab and near metal brackets for rubs or bare wires.
     
    Last edited: Oct 25, 2021
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  6. Goodysnap

    Goodysnap Road Train Member

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    Double post. Stupid phone.
     
  7. TortuousAugur

    TortuousAugur Bobtail Member

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    Sep 3, 2013
    Dallas, TX
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    Thank you. I'll give it a look once I've got time. Currently trying to make an impossible itinerary.
     
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  8. TortuousAugur

    TortuousAugur Bobtail Member

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    Dallas, TX
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    [​IMG]
    Not sure if this is what I'm looking for but I think that purple line is the same color as the one on the dump valve.

    Unfortunately, all of that is fairly segregated from my reach via the transmission and drive shaft on the underside and the engine and firewall on the top...

    I'm also hearing an air leak from the general area in there that I can't reach or do much about.

    On the bright side, I drove the truck quite a bit with the dump signal hose disconnected and I've not noticed that it's supplying air to the hose now. Knowing my luck it will start back up in a day or two, though.

    Also, the air leak I'm hearing in that area stops when I engage the dump switch in the cab.
     
    Last edited: Oct 27, 2021
  9. Goodysnap

    Goodysnap Road Train Member

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    Thats it. Very hard to access, yes.

    With the line hooked up may be leaking air out exhaust due to EOA not sealing off.
     
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  10. Goodysnap

    Goodysnap Road Train Member

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    We had one of these acting up just yesterday. If you have been in the shop for computer work or campaign work. 20PBC? It is possible a parameter in CECU can be switched for EOA control. ESA would be needed to correct this.
     
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  11. TortuousAugur

    TortuousAugur Bobtail Member

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    Sep 3, 2013
    Dallas, TX
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    It's not actually my truck and I've no clue what was done or not on the past. I've been driving it since late July and this issue is maybe in the last month or less.

    I've noticed in my time in the truck that whoever "maintained" the truck prior to me did nothing of the sort. I've got a video where I figured out I had to lay down on the ground to open the air drain valve (instead of the metal cord I'm use to) and when I opened it, I wouldn't be surprised if a quart of moisture came out of that tank alone. After my initial surprise, I got back to my feet, got inside the truck, got my phone, opened the camera, laid back down and started recording and it was still coming out as a heavy white mist. I'm surprised it didn't look like a water fountain, honestly. The other tank was similar but maybe better because I had drained the first one so much first.

    Just got done putting on 3 out of 4 fan shroud bolts so the fan wouldn't contact the shroud and 2 out of 4 coolant reservoir bolts so that it wouldn't rattle so much. Also noticed that the metal hose going to the radiator on top was rubbing the one fan shroud mounting bracket fastener so I had to zip tie that up on another piece of metal I had to replace a zip tie with a bolt to hoist it away from other stuff.

    Decent truck but there's so much that needs to be fixed, seems like. :confused:
     
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