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Gen 4 EGR cleaning at 360,000 miles

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by jerrymildred, Oct 21, 2022.

  1. jerrymildred

    jerrymildred Senior Member

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    Some time ago, before I started at this shop, a customer wanted his Gen 4 EGR cleaned at about 140k miles. I didn't get to see it, but I'm told is was super clean.

    This week we got in another Gen 4 for EGR cleaning. This one had about 360,000 miles on it. I will never again grumble about an EGR job on a Gen three. What a PITA that was!!!!

    Anyway, with 360k on the clock, those had to be lots of highway miles, so not a lot of EGR use, but that thing was really clean. Once we finally got it out of there.

    IMG_5632 Large.jpeg
    Gen 3 & 4 EGR coolers side by side. Lots more surface area in the Gen 4.

    IMG_5628 Large.jpeg
    Inside the Gen 4 cooler after a short blast with an air hose. I wasn't quick enough to get a picture before the air hose treatment, but it was just a little sooty.

    IMG_5624 Large.jpeg
    We had to remove several coolant hoses and electrical connectors and unclip the cables in order to pull the inverter out of the way to gain access to the nuts and studs holding the cooler in place. And hold it out of the way with a bungee cord.

    So, I'm thinking that if you have a Gen 4 Prius, you probably don't need to clean the EGR system, but if you choose to do so, brace yourself for lots of work getting it out and in but not much work cleaning it. :D

    And if you do/did clean one, maybe you could share your results? (y)
     
    #1 jerrymildred, Oct 21, 2022
    Last edited: Oct 21, 2022
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  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Wish there was a super-like button. (y)

    @Raytheeagle had similar “fun”, extracting EGR components on his prime.

    Sounds like they sorted out the carbon clogging. A stark difference from gen 3.

    The prodigal son parable comes to mind.
     
    #2 Mendel Leisk, Oct 22, 2022
    Last edited: Oct 22, 2022
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  3. ChapmanF

    ChapmanF Senior Member

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    Yes, that would be good. Gen 4 surely has the same built-in emissions monitor that you can ask about your EGR flow score any time you want, same as Gen 3. Starting a similar Gen 4 forum thread with some mileages and flow scores would be a way to get some very useful information, with a lot less trouble than bungeeing the inverter out of the way.

    My guess is that there will be some Gen 4s, maybe with fewer highway miles, that might show worse flow scores than this one did. (For that matter, it would have been nice to know the score for this one!)
     
    #3 ChapmanF, Oct 22, 2022
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  4. jerrymildred

    jerrymildred Senior Member

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    Indeed. I came in on it in the middle.
     
    #4 jerrymildred, Oct 23, 2022
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    This thread is maybe more interesting to third gen owners: 4th gen Prius, with all the lessons learned from third gen EGR, 360k miles, never had a cleaning, next to no carbon, and no head gasket problems.

    a couple of cold comforts:

    1. the #%*!# 3rd gen EGR components are easier to access (amazingly).

    2. our exhaust heat recovery components aren’t having coolant incontinence issues.
     
    #5 Mendel Leisk, Oct 23, 2022
    Last edited: Oct 23, 2022
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  6. ChapmanF

    ChapmanF Senior Member

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    Gen 4 cars have a different EGR system because the auto industry was researching a different EGR chemistry during the years Gen 3 was in design and production, and there are journal papers on the new chemistry, "catalyzed EGR", that were published during that time. Gen 4 uses that newer approach, which hadn't really been commercialized at the time Gen 3 was in design. Taking the gas from after the catalyst changes its chemical make-up and changes its effects on combustion, as the journal papers describe. And the components for catalyzed EGR have to be larger, because the gas from after the catalyst is of lower pressure. Everything must be proportionally larger to get the right flow.

    So there is a good deal more to the change between the Gen 3 and 4 equipment than just "lessons learned from third gen EGR".

    As this thread's in a Gen 4 forum, one hopes it'll stay interesting to Gen 4 owners, who can use it to collect their own data on how a wide sample of their own cars are doing (not all of which will have put on 360,000 miles in a handful of years).

    There won't be anything wrong with us Gen 3 owners peeking in, but we already have our own thread for Gen 3 mileage and EGR flow reporting. We can leave the Gen 4 folks a little space to have their own.

    @jerrymildred, what was the year of this 360,000 mile car?
     
    #6 ChapmanF, Oct 23, 2022
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  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Yessir...
     
    #7 Mendel Leisk, Oct 23, 2022
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  8. bisco

    bisco cookie crumbler

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    most gen 4 owners haven't a clue, unless they owned a defective gen 3
     
    #8 bisco, Oct 23, 2022
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  9. jerrymildred

    jerrymildred Senior Member

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    I was afraid you'd ask that question. :D I was going to ask several times but kept getting side tracked. I will try my best to remember to ask when I get back to the shop on Tuesday and then try my best to get back here with an answer. I'm curious about that, too.
     
    #9 jerrymildred, Oct 23, 2022
  10. CR94

    CR94 Senior Member

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    3. The 3rd-generation engine coolant pump is less difficult to replace, as I understand.
     
    #10 CR94, Oct 23, 2022
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