2012 egr cooler leaking

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by kevin mcfarland, Nov 3, 2025 at 4:45 PM.

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  1. kevin mcfarland

    kevin mcfarland New Member

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    Just purchase a 2012 started seeing white smoke and that sickening sweet smell of antifreeze burning, before looking to replace head gasket I unplugged the EGR vale and no more smoke, upon further research, and discussions w/ other mechanics the thought was even after replacing the cooler by driving car w/ EGR unplugged The car gets better mileage better performance, with check engine light on. the thought process is since you are not reburning spent exhaust you have a cleaner running engine with no worries about the port clogging especially on 1st cylinder causing notorious head gasket issues. Curious on other thoughts out there? When Cars due for inspection wipe code plug in EGR valve to inspect.
    Also I was considering even bypassing the EGR cooler antifreeze lines What would be the effect, bypassing the cooler while keeping the EGR unplugged?
     
    #1 kevin mcfarland, Nov 3, 2025 at 4:45 PM
  2. Brian1954

    Brian1954 Senior Member

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    #2 Brian1954, Nov 4, 2025 at 1:03 PM
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    I got kinda lost after that. What's the miles on it?
     
    #3 Mendel Leisk, Nov 4, 2025 at 3:17 PM
  4. rjparker

    rjparker Tu Humilde Sirviente

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    Unplugging the egr valve is highly unlikely to stop white smoke especially if was antifreeze (eg coolant).

    Unplugging the egr when the egr valve is closed (normally closed at low rpm and shutdown) will create a check engine light but not much else you will notice. I might do it except the check engine light on all the time will mask other problems. Other hybrid issues have their own warning lights. The overheating warning light is separate but often just flashes once or twice when it's all over except the crying.

    Yes there is coolant in the egr cooler but it is a stainless steel heat exchanger with the coolant separated from the exhaust gas flow. Even if your egr cooler was leaking internally (something that is almost unheard of), closing the egr valve would simply stop coolant flow to the intake manifold. A leaking egr cooler would continue to leak coolant directly into the exhaust system. This would quickly empty the engine coolant reservoir (passenger side) and soon cause engine overheating.

    The frequent cause of coolant burning is coolant entering a cylinder through a head gasket leak. These leaks can be infrequent at first but are almost always accompanied by a severe startup rattle when they happen.
     
    #4 rjparker, Nov 4, 2025 at 4:21 PM
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  5. kevin mcfarland

    kevin mcfarland New Member

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    112000 miles with egr plugged in on my 1st dive to work (60 miles each way) enough smoke (once I got on hwy) where I did not feel comfortable driving to work, turned around went home and drove my Camry in. Did not want to overheat. Motor had no miss no vibration or nothing other then smoke! I am a former mechanic, I was helping my brother putting a 4sp in his automatic 63 chevy when I was 14.owned 2 repair shops back in the day, besides my hobby building motorcycles when I was 16

    112,000 no miss or any vibration
     
    #5 kevin mcfarland, Nov 4, 2025 at 5:36 PM
    Last edited by a moderator: Nov 4, 2025 at 11:32 PM
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  6. kevin mcfarland

    kevin mcfarland New Member

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    112000 miles with egr plugged in on my 1st dive to work (60 miles each way) enough smoke (once I got on hwy) where I did not feel comfortable driving to work, turned around went home and drove my Camry in. Did not want to overheat. Motor had no miss no vibration or nothing other then smoke! I am a former mechanic, I was helping my brother putting a 4sp in his automatic 63 chevy when I was 14.owned 2 repair shops back in the day, besides my hobby building motorcycles when I was 16

    I have driven the car for about 500 miles w/ EGR unplugged and no smoke, no miss, no engines issues at all, nest week will retry plugging in the EGR valve to see what happens. Now I do not get the 50mpg as others get here, but I do get low 40's. I drive rather hard and hwy's around me are very steep hills, where the EV gauge is almost pinned climbing hills at 70MPH
     
    #6 kevin mcfarland, Nov 4, 2025 at 5:38 PM
    Last edited by a moderator: Nov 4, 2025 at 11:33 PM
  7. kevin mcfarland

    kevin mcfarland New Member

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    what my research is finding:
    According to Toyota deleting the Cooler 1) engine knocking- anti knock sensors correct that.

    2) Increased cylinder head temperatures? How would it increase head temps seeing as its exhaust gasses and I'm sure cooler would not cool exhaust temps that much especially at higher revs.

    3) Also increases vacuum in the PCV system, leading to oil rings getting caked with carbon and causing oil consumption problems. Unsure how closing the EGR valve increases PCV pressure? If it does then I can see how too much vacuum on PCV would suck oil vapors leading to excessive consumption if true?
     
    #7 kevin mcfarland, Nov 5, 2025 at 1:24 PM
  8. Tideland Prius

    Tideland Prius Moderator of the North
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    @kevin mcfarland please check your reply box before pressing “Post Reply”. You’ve made several duplicate posts.
     
    #8 Tideland Prius, Nov 5, 2025 at 5:09 PM
  9. kevin mcfarland

    kevin mcfarland New Member

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    sorry OK
     
    #9 kevin mcfarland, Nov 5, 2025 at 7:30 PM
  10. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Exhaust gas is oxygen-depleted, which quenches combustion. When it clogs, and it's often asymmetrically, it's cylinder one that tends to fully clog first, and it's the common wall between cylinders one and two that the coolant tends to leak first, into the cylinder one side. The computers see still-decent flow, have no way of monitoring individual cylinder flow, and cylinder one, with more oxygen in the mix, combusts "better".

    The EGR cooler lives up to it's namesake, IF it's internal radiator fins are not coated with a layer of (insulating) carbon.

    That's a fair bit of card-castle logic...

    Toyota spec'd oil rings with low outward springiness (until they capitulated mid-way through model year 2014), which appears to be the cause of oil consumption. The PCV valve, even when working optimally, is always dumping dreck into the intake manifold. An oil catch can helps, some.
     
    #10 Mendel Leisk, Nov 5, 2025 at 7:31 PM
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