Time for a DPF bake? Excessive and long rolling regens

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by zaroba, Oct 2, 2022.

  1. zaroba

    zaroba Heavy Load Member

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    South East PA
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    2916 t680, paccar mx13, 648k miles.

    Used to do a normal 5-10 min rolling regen after idling all night. But it has turned into a half hour rolling regen and it only takes a few hours of idling to require one. After 3-4 hours of driving will do another, and a 3rd after another 3-4 hours of driving.

    These rolling regens come with excessive smoke. If I stop at a red light or stop sign smoke will be billowing out from under my truck and around my hood looking like I lost a coolant line. A few times when it started I pulled over thinking I had an issue but the regen stops once brakes are set so the smoke stops. Looked over the whole exhaust line and can't find any leaks, the pipe clamps are all tight and the exhaust pipes are good.

    Parked regens are still the normal 10-15 mins without excessive smoke, but if I idle long enough to require and do one, the truck will still immediately do a long, smokey, rolling regen when I start driving.

    Hooked up my davie 4 and there's no engine faults and there doesn't appear to be any negative engine performance so I assume purely a DPF issue.
     
    Last edited: Oct 2, 2022
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  3. Goodysnap

    Goodysnap Road Train Member

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    You have an exhaust leak, fix that first. Most commonly the main exhaust bellow or flex pipe under the cab with the high mount exhaust.

    Clean or replace the DPF your choice and I would throw a DPF pressure sensor on for reliability if it’s never been replaced. Engine management sensor cleaning and clean and service the Fuel doser.

    All these items done properly will put her back to normal.
     
  4. spsauerland

    spsauerland Road Train Member

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    Have your DOC cleaned or replaced too. Whitish smoke during Regen (raw fuel) is indicator that fuel is not being oxidized across DOC and DPF.
     
  5. Arctic_fox

    Arctic_fox Road Train Member

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    Do everything goodysnap recomended buy also have them change your EGR valve as well. If you have been blowing smoke for a while and the valve is worn it can cause it to seize up even after being cleaned hence the smoke issue. I would also guess your system is contaminated so i would have any sensor in or along the exhaust line pulled and cleaned as well as your EGR pipe pulled and cleaned. Also have them check the turbo just to be safe an ensure there are no major buildups of soot that could destroy it.
     
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  6. bzinger

    bzinger Road Train Member

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    Yes and the sooner the better ! I didn't know mine was leaking until it melted the air lines going into my transmission.
     
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  7. D.Tibbitt

    D.Tibbitt Road Train Member

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    what would it mean if there is a blueish color smoke that comes out for a couple seconds while the truck is regening going down the highway?
     
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  8. spsauerland

    spsauerland Road Train Member

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    Blueish/white is usually raw fuel that didn't react with the DOC and DPF.
     
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  9. JonJon78

    JonJon78 Road Train Member

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    Whats the average lifespan of a DPF pressure sensor? Or at what mileage are they recommended to be changed out at?
     
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  10. Goodysnap

    Goodysnap Road Train Member

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    Nothing concrete really. Most line haul trucks I would say start acting up around 500k. Vocational maybe 200k. I can tell you that I replace a lot. They can really be tricky to pick out even for a well trained eye. The regen history will tell a story. Drastic changes in the pressure reading from one regen to another in the history is a telltale for sure. The DPF pressure should be a gradual increase. Not sudden changes in pressure from 1 regen to the next.

    The sensor can become biased pressure but still function in range and cause random frequent regenerations even though the pressure is really normal.

    Many times I have seen DPFs cleaned and or replaced only to end up replacing a bum sensor for frequent regens.
     
    Last edited: Oct 3, 2022
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  11. zaroba

    zaroba Heavy Load Member

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    Thanks for all the info guys. I'll look closer for a leak. It never crossed my mind to stop while it's doing a smokey regen and just set my trailer brakes so the regen continues and looking for where the smoke is coming from to find the leak so will try that after delivering this load. Shouldn't be hard, idle all night at a rest area to make the rolling regen happen and stop in a truckstop while it's doing it.

    As for getting it done soon, well, it's been happening for almost a year now so 'soon' is well past, sadly. I just didn't have the money to look into fixing it due to real life stuff. Not trucking related except PennDOT almost ruining me. I almost had to sell my trailer to keep my truck but back on my feet now.
     
    Last edited: Oct 4, 2022
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