broken thermostat bolt

Discussion in 'Gen 3 Prius Main Forum' started by mhdriver, Jan 14, 2026 at 2:02 PM.

  1. mhdriver

    mhdriver Member

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    Yeah, I'd say the epoxy is useless. Calling a mobile welder.
     
    #21 mhdriver, Jan 16, 2026 at 10:47 PM
    Last edited: Jan 16, 2026 at 10:58 PM
  2. douglasjre

    douglasjre Senior Member

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    A mechanic has a big mental tool bag of skills. You need to use AI to get a list of the possible methods. Problem is you haven't the muscle memory of any of these skills and you don't have the tools.


    Solutions:
    1. Electromagnetic induction heater: Magnetic Induction Heater Bolt Removal https://a.co/d/0ZqvJ1Y

    2. Weld a nut onto it and use that plus heat

    3. Use grinding wheel to grind bolt flat and used hi carbon steel bits purchase anywhere except harbor freight after using a center punch to drill into that bolt with left-handed drill bits and then an easy out

    4. Cut a piece of aluminum off and TIG weld in other piece of aluminum on drill it and start over
     
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  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Eric the car guy weighs in:

     
  4. mhdriver

    mhdriver Member

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    Bought a 3 in 1 welder from Amazon. Should have it tomorrow. I took the wiring harness in that area off. I have enough room to weld a nut on that bolt from the side. I'll also get the bolt cherry red hot, which ought to help. Tomorrow is the big day. My Prius seems to have a lot of brittle bolts. I'm getting the tools in place to deal with them.
     
  5. indel

    indel Member

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    You are now entering very dangerous territory. Safety is paramount. Please protect your precious organs. You can always buy another Prius, your eyes is another story. I know you know this already, but it helps to have someone else restate it for you.
     
  6. Hayslayer

    Hayslayer Active Member

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    I don't want to be a debbie downer, but I have a bad feeling you're about to wreck this thing. There comes a time when you fold your cards and seek experienced help. F this up and there's no easy or inexpensive next try. I have yet to break a bolt on a Gen 2. Although I have no idea what you may have spent for an amazon welder, it's likely more than it would have cost to have a pro get it out. I wish you the best of luck.

    Quick edit.....I am wrong about one thing for sure. I just looked up welders on Amazon...never realized anyone could sell a "3 in 1" welder for 80 bucks. Bet it's a champ, but definitely cheaper than a pro mech or mobile mech..at least in the short term.
     
    #26 Hayslayer, Jan 19, 2026 at 9:44 PM
    Last edited: Jan 20, 2026 at 8:28 AM
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  7. indel

    indel Member

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    I agree with Hayslayer. It might even be worth having a reputed mobile mechanic come to you.
     
  8. Tombukt2

    Tombukt2 Senior Member

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    Well reputable mobile meccie . I'd rather play around on my own dime an expert isnt going to make lotsa difference . He wouldn'tve broken the mess. Toyoda bolts aren't brittle . Good rule on old stuff . Tighten one click first. Then reverse out by hand . Don't always reach for automatic tooling.
     
  9. indel

    indel Member

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    Yes, but you play with cars all day long. Not the guy who is in a bind. As much as I hate taking my car to a mechanic, I would not hesitate to do so for certain things.
     
  10. mhdriver

    mhdriver Member

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    With all due respect, you're making WAY too muich drama out of this. Don't you think I'd have a welding helmet and practiced several simulations before I tried it? It's not rocket science, just something I was unequipped to address. As a long term RN, the #1 way people get seriously injured working on cars is having the car fall on them. Not an issue here. This is a tiny weld, granted in a tight space, but very doable. Question is after I weld it, is it going to come out or will the rest of the bolt sticking out twist off? If that happens, I'm going to have to drill it out. Not my first choice, but doable.
     
  11. mhdriver

    mhdriver Member

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    I spent $119 on the welder. $40 on a helmet. This is a tiny welding job. Taking off the water pump and the thermostat, I've had a total of 3 bolts break. I'm not doing anything except wrenching them off by hand. My car was up north for about 7 years. No visible rust on the body, but some rusting underneath. All of the bolts on the skid plate are rusted and snap if you try to take them off. All the bolts that broke are 6mm, I think (about 1/4 inch). The bigger ones have been fine. I got a welder who wants $250 to come out, no guarantee of success, other than he'll weld a nut on the bolt. I figure I'd rather have the tool for the next time I need it. Buying a 4 post car lift in another couple of months, just put up a 30 x 80 garage. Yes, I could pay to tow the car but not my way of doing things.
     
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  12. ASRDogman

    ASRDogman Senior Member

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    Perhaps you only see those people......
    As a technician.... I've NEVER seen a car fall on someone.
    Busted knuckles is #1.....

    I hope your welding works. Perhaps an inductive heater would work better?
    Make sure you clean the area of any oils that could catch fire.....


    As a long term RN, the #1 way people get seriously injured working on cars is having the car fall on them


     
  13. indel

    indel Member

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    It's obvious you know what you are doing. Let us know how it goes.
     
  14. mhdriver

    mhdriver Member

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    Believe me, it's not pretty. When you've had a patient like this, you remember it. It's a life-changing injury. I don't really know the exacts of where these guys were working, but I'm sure they weren't in a well equipped shop. You see some pretty serious injuries and it makes me think twice when getting under a car or on a roof or running a chainsaw. It's always worth it to buy protective equipment. We're building a house next year, I'm buying the sticky roof shorts and wearing a harness. If you have a guy paralyzed from the waist down, his whole life froze the moment he fell off the roof. He relives that fall every day. You want to cry for him but there's only prevention, never cure.

    I did some stick welding yesterday to simulate the job, but my little gun stick welder off Temu doesn't have the oomp to sustain a weld. The stick got stuck 95% of the time without getting a weld going. So I bought this and upped the game. I'm going to be trying several bolts on the ends of nuts with this flux core mig welder. It also does stick.
     
  15. Mendel Leisk

    Mendel Leisk MMX GEN III

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    For insurance, getting under a car, if it's possible (and it usually is), I push this under first:

    IMG_3044.jpeg
     
  16. indel

    indel Member

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    I like to get it on jack stands at the pinch welds and then I place my floor jack on the front lift point, raised just enough so it makes contact and lock it. Catastrophic failure at 3 points is pretty unlikely.
     
  17. Mendel Leisk

    Mendel Leisk MMX GEN III

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    I use alternates to the pinch welds, see oil change link in my signature. (on a phone turn it landscape to see signatures)

    Food for thought: if you put the scissor jack at the "pinch weld" location, and start it up, you'll see it's not actually the pinch weld that's bearing on the scissor jack; the jack cradle has a notch that cups around the pinch weld, and the bearing point is on the inside, beyond that vertical seam, just the regular car body sheet metal. And that point dimples in with even one use, as I found, using it just on a rear corner (with a flat, out and about).

    Decent pic of the front points I'm using here (in those pics I'm still using pinch welds for the rears, but I've long since stopped doing that as well), and on page 2 of that there's mention of the alternate rear points I'm using. The latter are basically on the humps where the locator pins are during shipping, where you see those oblongs slots with rubber plugs.
     
    #37 Mendel Leisk, Jan 20, 2026 at 12:49 PM
    Last edited: Jan 20, 2026 at 12:59 PM
  18. rjparker

    rjparker Tu Humilde Sirviente

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    The problem with beginner welding is you could permanently fuse the bolt into the block or melt the aluminum. You have already stated access is difficult.

    The advantage an experienced auto shop has is they have plans a-z to get it out, have the best tools, muscle memory based on years of experience and a high likelyhood an easier method like acetylene heating and specific tools will get it out in ten minutes.