EGR Cooler "Nightmare Nut" Removal

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Sage C, Jul 22, 2026 at 2:04 PM.

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  1. Sage C

    Sage C New Member

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    Hi! I'm working on taking apart my 2010 prius EGR system, I have the intake manifold, throttle body, the EGR metal hose that attaches to the intake manifold, and I have all the nuts/studs off, *except* the nightmare nut underneath the cooler. Does anyone have any tips on the length of wrench, length of socket, *anything* that can help me get this dang thing off?
     
    #1 Sage C, Jul 22, 2026 at 2:04 PM
  2. PriusCamper

    PriusCamper Senior Member

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    You can check @Mendel Leisk posts as he has links on how to do that job in the signature line of all his comments. His suggestion for that nightmare nut is to work on getting that one loose prior to the day of doing the job. I'm about to dive down into the Gen3 EGR rabbit hole and start doing them regularly and my plan is to have a clean EGR and cooler ready to go so I just swap them rather than having to soak and wait for them to be clean... Seems like that's the strategy of more than just me, lol...

    EGR.png
     
    #2 PriusCamper, Jul 22, 2026 at 9:00 PM
  3. Georgina Rudkus

    Georgina Rudkus Senior Member

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    As I recall, it is an external torx net, either an E8 or an E10.

    External torx nuts are commonly used in German cars like BMW and Mercedes.
     
    #3 Georgina Rudkus, Jul 22, 2026 at 9:11 PM
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