Another EGR thread

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by darknd666, Apr 1, 2026 at 12:01 AM.

  1. darknd666

    darknd666 Junior Member

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    To start off, I just got this car and successfully fixed the brake booster failure. Now sonce Ive been driving it all the real problems have been coning out of the woodwork. I diagnosed it down to the puddle of oil in the intake manifold. Ive researched enough to know this is a known problem. The symptoms were knocking and shaking at 50% power and 20-30mph with mild shaking at higher speeds. No coolant or oil loss that I can detect from 300 miles of driving.

    So I have already:

    1. Removed the intake manifold, throttle body, and EGR components.

    2. EGR was definitely on its way to becoming fully clogged. The pipe had a significant amount in it as well. The EGR cooler was brake cleanered down with 2 cans and a pressure wash in between. It looks damn close to new now with significantly more light and air oassing through after cleaning, yes I tested both air and light passage. No abrasive scrubbing was used in the EGR.

    3. Cylinder ports were brushed out and vacuumed to the best of my ability. Bottom line they are cleaner than before but definitely not perfect. Walnut blasting woukd be preferred but its whatever.

    Still yet to accomplish in the coming days:

    1. Brand new intake manifold coming in the mail, non-OEM but supposedly is redesigned. Hopefully it helps. I have researched the differences between the manifold part numbers visually. If I find it to be modeled after the revised *54 part number ill use it if not ill just clean the original to the best of my ability and use it.

    2. Spark plugs, replacing them with new NGK rhutheniums. Yes they are fancy, I run them in my Yaris. They should allow a more complete burn (manufacturer claim). Upon inspection they are as cooked as the rest of the intake components.

    3. Oil catch can. This is from what ive read the most effective method of combating this design flaw. Coming in the mail soon.

    4. Software update for the EGR valve control. supposedly there was a TSB for the intake manifold that this accompanied. I read it mitigates the opening of the EGR to diminish the carbon buildup including the baffling system in the redesigned intake manifold. Maybe Toyota will do it for free if the TSB is valid. Hopefully they dont decline when they see my catch can .

    Things up for discussion:

    1. Intake manifold redesign. The new design is not conducive to enhanced performance and in fact the baffles probably make it worse. If i can source some other performance intake mods that are budget friendly it would be appreciated. Something to help compensate any performance loss. Maybe MPG increase, IDK. Its still prius slow, im jn it for the MPGs ⛽.

    2. This is a 2012, so early design issues are a common theme. Im totally fine with replacing a motor when it comes time, if the community agrees a late year gen 3 donor would do right? When the piston rings inevitably fail.
     
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  2. Brian1954

    Brian1954 Senior Member

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    The dealership will not update the ECM software for free. They will do it for $200 to $250 depending on the labor rate the dealership charges. Ask your local dealership for a quote to have it done.
     
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  3. 2015V-BadHG

    2015V-BadHG New Member

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    Thx for the EGR info.
    We have a 2012 Ct200h and a 2015 V model3 . Did HG , EGR cleaning , water pump and tstat on both.
    V I just go a brand new off brand intake, haven't installed it yet.
    I did want to add to his that I believe the more cold weather/climate driving you do the worse the EGR clogging up is.

    The CT seems to less stop/start then my V and its EGR wasnt as bad.

    Pete
     
  4. darknd666

    darknd666 Junior Member

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    I just had an excellent idea to throw around here...what if I helad an exhaust shop relocate the EGR exit on the exhaust side to be after the Catalytic converter, like how it is on the Gen 4? Would that further reduce the problem or introduce new problems such as EGR exhaust temp and CELs?
     
  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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    What's the miles on it?
     
  6. darknd666

    darknd666 Junior Member

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    197k miles
     
  7. Mendel Leisk

    Mendel Leisk MMX GEN III

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    I'd back off on the parts cannon, check condition of head gasket.

    EGR cleaning is good, but belated. A soak with a caustic solution (KOH or NaOH) is much more effective than brake cleaner, for just the cooler. Brake cleaner with brushes and rags will suffice for the rest, and you don't want to use caustic cleaner on anything but the cooler, which is stainless steel. New intake manifold is not going to help. But focus on head gasket first.
     
    #7 Mendel Leisk, Apr 1, 2026 at 10:55 AM
    Last edited: Apr 1, 2026 at 11:01 AM
  8. ChapmanF

    ChapmanF Senior Member

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    You would then get insufficient EGR flow, because of the lower pressure of the exhaust behind the cat. You could also replace the cooler and valve with the gen 4 versions, which were upsized so they can carry the proper EGR flow at the lower pressure.

    The chemical composition of the exhaust after the cat is also different, and has different effects on combustion, so there may be differences in the ECM programming about how much to use and when. I can't say how significant those differences might be.

    The whole idea of using "catalyzed EGR", and what exact changes would be needed to do it, was an active research topic industry-wide during the gen 3 years. The necessary knowledge was in place in time for gen 4.
     
  9. darknd666

    darknd666 Junior Member

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    How will I know if its a head gasket?
     
  10. darknd666

    darknd666 Junior Member

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    Is there a thread for this mod?
     
  11. ChapmanF

    ChapmanF Senior Member

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    You might have the privilege of starting the first.

    If it were my project, I would want to start at a library and snarf up everything I could about what automotive researchers learned would have to change in EGR systems to use exhaust from after the cat. That research was going on around the early 2010s.

    You might find some good information in Toyota's New Car Features manual explaining the gen 4 changes to EGR. (The information there will be pared down and simplified, enough for technicians to understand the basics, not so much for engineers to design or evaluate mods.)

    Toyota Service Information and Where To Find It | PriusChat
     
    #11 ChapmanF, Apr 1, 2026 at 11:18 AM
    Last edited: Apr 1, 2026 at 11:24 AM
  12. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Miles alone is 90%, but confirmation typically entails borescope inspection, preferably with engine coolant system pressurized, morning after a previous day with driving. A borescope that can look "over it's shoulder is good. You're looking for coolant pooling atop pistons, exceptionally clean pistons, beeds of coolant forming at the head gasket seam and/or running down the cylinder walls.
     
  13. darknd666

    darknd666 Junior Member

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    I have an endoscope, the spark plugs are out, seems like a fine time to dive in there and see what it looks like.
     
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  14. Mendel Leisk

    Mendel Leisk MMX GEN III

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  15. darknd666

    darknd666 Junior Member

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    It knocked real good for a few seconds on a cold start once when I bought it and hasnt at all since then. But the conditions I described in the first post are still there. If there is a head gasket leak its very small as I have not noticed any coolant leak. This was all with 300 miles of highway driving around 70mph. I had it in ECO mode and tried my hardest not to push the motor too hard on the throttle.
     
  16. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Just caught on to this: it's very common for 3rd gen Prius to have head gasket failure, most often starting around 150k miles. Seller may have been dumping stop-leak product into the coolant, then gave up on it, added another bottle, put it up for sale.
     
  17. darknd666

    darknd666 Junior Member

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    They sold it because of the brake booster failure.
     
  18. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Could be some misdirection at play, disclosing one problem distracts from another. LIke that the magician who "let's you in one one trick", while pulling another.
     
  19. darknd666

    darknd666 Junior Member

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    Im hoping upon inspection, ive caught this issue before the head gasket blows. But it being all aluminum, it doesnt take much overheating to cause warpage and leaks in the head.
     
  20. darknd666

    darknd666 Junior Member

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    Could have just been neglected. As stated if I have to swap in a 2016 I will.