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EGR Cooler/Valve Question

Discussion in 'Gen 3 Prius Main Forum' started by PriusGuy32, Jan 12, 2022.

  1. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Just bought my FIFTH Prius, lol. Its a 2015 Prius Four with 83,000 miles and an excellent Toyota service history of dealer oil changes every 5,000 miles.
    It sounds different than my last Gen3. When it starts up - hot or cold engine - it doesn't sound smooth. I dont want to say it rattles, but it definitely makes some kind of noise for a split second. Im wondering if, at 83k miles, my EGR Cooler could be clogged? What is the mileage recommendation for cleaning it?
     
  2. ChapmanF

    ChapmanF Senior Member

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    There are a few different ways the EGR system might contribute to engine roughness, and those would have different implications for you.

    (1) The most direct way would be if the EGR system sticks open. If it allows EGR to flow at times, like startup or idle, when the engine isn't working hard enough to handle it, that will directly lead to rough running. Note that this situation is pretty much the opposite of an "EGR clogged" situation. It could be caused by deposits on the valve though. If that's the story, then it's the direct cause of the rough running, and if you fix it, the rough running goes away.

    (2) Another direct effect is seen if the four separate EGR passages in the intake manifold itself to be clogged up by different amounts (the ECM has no way to tell that has happened). In that situation, you typically won't have roughness at startup or idle (the valve is closed then anyway, unless it is stuck open as in (1)), but then at moderate loads you might notice some roughness sneaking in as the valve starts to open, and then the cylinders get different mixes of gas. Again, if that is happening, you correct the issue and the symptom goes away, done.

    (3) An indirect way that is often conjectured here on PriusChat is that clogging of the EGR system could eventually result in head gasket damage, and then the leakage of coolant into the cylinders through the blown gasket gives you a rough startup. I have my questions about the strength of that conjecture, but it has very strong adherents on PriusChat who are probably typing at the same time I am. :) It is important to remember that, if that is the story, then it is not an EGR problem at this point causing your engine roughness, and nothing you could do with the EGR at this point would fix it. Something about the EGR in the past might have contributed to head gasket damage, but once the gasket is blown, it's blown, and if coolant entry through the gasket is what's roughening the startup, there is no way around having to fix that problem.
     
  3. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Thanks Chapman. You know, after owning 4 Gen3's, I have never owned one long enough/had one high mileage enough to ever clean the EGR circuit? What is the mileage I should do the "1st cleaning"? Im at 83,000 miles currently.

    Also, I remember the MAF affecting my Gen2 and needing (2x year?) cleaning with special MAF cleaner spray. Is the Gen3 susceptible to the same issue?
     
  4. ChapmanF

    ChapmanF Senior Member

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    The Gen 3 does have a MAF sensor, and it can still cause poor running if it gets dirty. i've never ever ever heard of one needing cleaning twice a year—what on earth kind of conditions were you driving through?

    EGR cleaning—the folks who are big on the "it will always clog and destroy your head gasket" conjecture might have a schedule for you. Another very easy option is to just ask your car now and then what its most recent EGR flow self test numbers were, as seen in this thread. You can see there what ranges of numbers you might expect at different mileages.

    Brand-spanking-new-shiny seems to give numbers around 20 or 21 kPa. Mine was down to around half that, as of last summer when I cleaned it, and that was around 155,xxx miles for me. We don't really have data to give you a rule for how low you're comfortable letting that number go; if you decide, for example, you don't ever want to let your numbers go below what mine were, then you can watch yours and decide to clean when the numbers get there, which could come at a different mileage for you than it did for me.

    I've been suggesting people combine that strategy with actually taking off the intake manifold from time to time and looking at the small EGR passages there. The ECM's test results are incapable of telling you what's going on there, and out of all the variants of EGR ⇒ gasket damage conjectures going around, that's probably the one I'd be most prepared to give some credence to. And taking off just the manifold for that much of an inspection is a very easy job. Doing the whole upstream EGR path is not.
     
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  5. xliderider

    xliderider Senior Member

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    At 124K, our EGR cooler was about 75 percent blocked. Likewise, the worst two (at intake 1 & 2) of the EGR passages in the intake manifold.

    My advice? Install an oil catch can between the PCV valve and the intake manifold to catch some of the oil that enters the intake manifold. The oil and oil vapor combines with the sooty EGR gases and really makes a gunky mess in the intake manifold.

    The EGR cooler I got off eBay to pre clean and swap with the EGR cooler on my Prius was completely blocked with oily/sooty gunk, similar to the stuff that accumulates in the intake manifold, so I'm guessing that it came from a high mileage Prius that was burning a lot of oil that went through the combustion process and the oil also ended up in the EGR valve and cooler.

    Keep the oil out of the intake, and I'm betting that subsequent cleaning of everything from the EGR valve, cooler, and intake will be much easier the next time around. I'm sure your catalytic converter will be much happier too.

    Posted via the PriusChat mobile app.
     
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  6. Tombukt2

    Tombukt2 Senior Member

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    So on the 65K engine that I've got sitting here on the ground I need to take off the intake manifold Make sure all the ports are whistle clean check the EGR path up to that point intake manifold Make sure all that's clean put it back together and put a catch can in between the PCV and its feed. We'll catch Can's ive got. I guess the can needs to go low so the vapor will flow down drop the oil and then get sucked up to the PCV? Well right now I've got to figure out how to get that 2013 into neutral and get it up on a tow dolly to get it over to the shop where we're going to pull the motor and tranny in put in the new one I got the park on level surface screen it's only running when it does run on three cylinders number two is zero compression and sometimes it sounds like something's banging in the bell housing or the space between the motor and the engine probably just seriously out of balance because of the one cylinder having zero compression but anyway that's where we're at
     
  7. ChapmanF

    ChapmanF Senior Member

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    If you can get twelve volts to it and go to IG ON (two button presses, no brake), just shift to N. Then pull the P CON MAIN fuse before you power off so it can't go back to Park.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    83K is a good time to have a look. Info in first link in my signature.
     
  9. Abarnabe

    Abarnabe Member

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    If you shut down while the ice is charging from 40 to 50% the next start up it will rattle, it's a known bug. try waiting until the ice stops charging before shutting down.
     
  10. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Can you recommend a catch can? I've never installed one on my other Gen3's, but with this one being the highest mileage one, I will. Thanks.
     
  11. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Just quoted to get your attention: I read the other thread regarding Tech Stream (Which I do have), and the EGR Flow Insufficency, etc... so I went out earlier and took this shot from my laptop screen. Can you tell me what you think of the numbers?

    thumbnail_IMG_3718.jpg [​IMG]
     
    #11 PriusGuy32, Jan 13, 2022
    Last edited: Jan 13, 2022
  12. ChapmanF

    ChapmanF Senior Member

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    For some reason, I see two red broken-image X marks there, but one of them I can click and see an image, and the other isn't clickable. The one I can see looks like this:

    thumbnail-IMG-3718.jpg

    If you look through the EGR flow data thread, you will see that a number like yours, 20.17, is about as good as it ever gets. Higher is better; 21 point something is what I got last summer immediately after swapping in whistle-clean shiny parts. My numbers were down to ten point something at 155,000 before I did that work. I think gromittoo did the work a bit earlier, 14 or 15 or so.

    I think if I were looking at 20.17, I would be scheduling other car-improvement projects ahead of fussing with the EGR.

    It can still be worthwhile to pop the intake manifold off for a look. adonturia had rough-running symptoms that were cured by cleaning out the manifold passages even though the overall flow result was a nice healthy 19 to 20 kPa before and after. The manifold by itself is not a difficult job.

    (It still requires attention to detail. There was a recent thread referring to a video that showed a Lexus with an engine rattle that was caused by somebody doing a manifold or EGR cleaning job and leaving two bolts out in reassembly. :))
     
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  13. Tombukt2

    Tombukt2 Senior Member

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    The intake manifold is plastic correct That's I think what I'm seeing. So if I was to remove the intake manifold . I'm guessing I'm going to see some ports for the EGR that will line up with ports on the aluminum head and that EGR flows through these ports I am in North Carolina and NASCAR country and people around here have forced putty abrasives commonly called like extrude home I might could take the manifold over there and have them push 2 thou out of it I don't know how much there is to push. For the wall sickness of the plastic manifold I was just wondering if while I had it off it would be worthwhile to open those ports up say 25 thou . Just a little more room to clog up slower is all I was thinking and then of course I guess I need to ream the porch to go into the aluminum head I don't know the layout of this thing so I guess I'll see when I take the intake off
     
  14. ChapmanF

    ChapmanF Senior Member

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    No, altering the designed dimensions of the manifold doesn't strike me as a very good idea.

    There are four little passages in it. You see them in the bottoms of the four ports to the head; they simply join up there.

    The passages get some carbon in them. You can knock the carbon out with any kind of stiff thing you can work through the passages. I used a length of nylon vacuum line from an old Ford. Some people post about going to much more elaborate lengths, but my goal is not to host state dinners in my intake manifold. It's to knock a good amount of the carbon out and then go do something else.

    Keep in mind that even the likeliest badness resulting from the carbon in the first place is not that the passages get restricted some; it's that they get differently restricted. They're still going to start getting carbon again as soon as you're done with the job, whether you enlarged them or not, and the enlargement won't change anything about the differently restricted part.
     
  15. philr

    philr Junior Member

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    Unsure if there is a factory recommendation for service on the cooler but I combined it with the service for 100K Spark Plug Change, Coolant Change, PCV Change, EGR and Pipe Clean, Intake Manifold Ports Clean w gaskets - and did the water pump and thermostat too. Glad I did as the EGR cooler was 75%+ blocked and lots of carbon in the EGR and Pipe.

    To clean the cooler, I plugged the one end and filled it with a product from Amazon called Carbon Off. I let it sit full of this product over night and the Carbon Off level had dropped (so I assume that it opened up plugged channels). While the level was down, I used a small diameter wire (smaller than a coat hanger wire diameter) to poke through the many cooler channels then refilled it for another overnight soak with the carbon off. The second day I drained out the Carbon Off and soaked the cooler in a bucket of hot water then used a garden hose to flush it out, used compressed air to blow it out then checked all the channels with the wire again and put it on the shelf for the next 100K service.

    Phil
     
    #15 philr, Jan 22, 2022
    Last edited: Jan 22, 2022
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