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Thread: Loosening stuck bolts w/o shearing?

  1. #1
    Mad scientist DrWin's Avatar
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    Question Loosening stuck bolts w/o shearing?

    So, I need to remove the valve covers and the coolant Y-pipe in the VOD. Legend has it that I could easily shear one or more of them. Poking around on this site and elsewhere, I get the impression that there are several ways of removing the stuck bolts. Or at least making it easier, all have to do with heating/cooling.
    (I suppose we are exploiting the difference in thermal rate of expansion between the steel bolt and the aluminum engine block?)

    • Heating with propane torch.
    • Heating by shorting a car battery through the bolt.
    • Heating with induction, special tool.
    • Cooling by cold spray from a can. (It's cold! It's damn cold!)


    I'm partial to going with the special induction tool or the spray can, since it seems easiest to control.
    Could someone advice what your prefered methods are, what works best, and especially if any of the above mentioned have gone wrong/should be avoided?
    Please excuse the crudity of this DeLorean as I didn't have time to repair it yet.
    VIN 10207 - December '81, Gray Interior, 3-speed automatic, stock PRV engine.

  2. #2
    Senior Member Gregadeth's Avatar
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    This works pretty well:

    Blaster 16-PB Penetrating Catalyst - 11 oz. https://www.amazon.com/dp/B00XOSYNM6/
    Last edited by Gregadeth; 01-21-2022 at 03:34 AM.

  3. #3
    Senior Member
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    I think the induction tool would be best although Iíve never used one. It might be hard to use in some locations. A actalen torch is probably the quickest, but it also can be hard to use in certain locations. A propane is not so good because you have a lot of heat in the area before you get the bolt/nut red hot. Iíve used the battery deal with great success. It would be nice to build a proper setup. I only used some old jumper cables.

    I watched a utube video where they compared penetrant sprays. I canít remember the best one, but I couldnít get it locally. (PB and WD were not at the top of the list)

  4. #4
    Senior Member SupercoolBill's Avatar
    Join Date:  Oct 2021

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    Been breaking bolts left and right on my project. A buddy just gave me one of these to try. 20220121_071033.jpg

    Sent from my SM-G970U using Tapatalk

  5. #5
    Senior Member 82DMC12's Avatar
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    I don't have any experience with cold sprays or induction. I'm curious about them though and would try them, given the opportunity.

    Most of my research seems to indicate that a mixture of 50/50 acetone and auto transmission fluid is a very good penetrating oil. There is also a spray called Aerokroil which is fairly expensive but seems to be known as the best retail spray there is. Hard to find but it's on Amazon. I bought some this year while doing a full front and rear chassis refurbishment and VOD project and so far I've been very happy with it. It was recommended to me by a mobile truck repair technician.

    https://www.amazon.com/Kano-Aerokroi...dp/B000F09CEA/

    I've also used MAP with a Bernzomatic TS8000 swirling burner and that works pretty well too. Acetylene is apparently "the best" but not easy for a Sunday shadetree guy to get a hold of in a pinch. Many hundreds of dollars in equipment just to get set up for something you will rarely use.

    So, for the regular guy wrenching, my suggestion is an oil can with 50/50 acetone + ATF, a can of Aerokroil, and a good quality MAP torch. But for real, patience is the main thing you need. Recognize which bolts are likely to be a problem and soak them for a couple days first. Spray them twice a day until GO TIME. Strike the bolt head squarely with a hammer every now and then to loosen them up. Hit the surrounding metal (NOT the bolt head) with some heat, and then try to turn them out. Best to use a 6-point socket and turn the bolt hard the first time. If you try to go slow, it's more likely to twist the metal so it breaks. Give it a good firm turn so it shocks loose. If it's still feeling tight, spray more penetrating oil and wait. Then turn it out maybe one full turn, then back in half a turn, and go back and forth between those two points with the ratchet until it's moving freely. Then go another half turn or full turn past that point. Stop, and turn it back into the hole, back and forth until it's loose. And keep coming out like that. Just a bit further each time.

    Get the bolt out, blow the hole out with compressed air, and replace the bolt if it's at all rusty or suspect. Oil the new bolt with cutting and tapping oil and run it in a couple times to make sure the threads are good and lubricated. That way you don't make things worse and you'll be less likely the crossthead when re-installing.

    If the threads are open on the other side, like for example the holes that you screw the sway bar into the front frame extension, spray both sides of the bolt. And that would be very easy to chase the threads out with a quality thread tap before re-installing. There is a special tap for blind threaded holes but I don't own any of those.
    Andy Lien

    VIN 11596 Jan 1982 build - owned since Nov. 2000!

    Photography and Backpacking is life.

    Was Fargo, ND
    Now Olathe, KS

  6. #6
    Senior Member
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    The reason the bolts break is that you have plated steel bolts in aluminum and eventually the plating on the bolts corrodes allowing the steel and aluminum to corrode together. Hard to know which bolts will break, some will come out easily and others will just twist right off. Even with precautions you can easily break bolts. My favorite method is an acetylene torch but you can't always use it because of combustibles nearly or heat sensitive materials. Sometimes sprays and liquids can be helpful but it is always hard to get them where they need to be. They seem to work better once you can get the bolt to move even if only a little. The best advice is when you take the bolts out, turn them back-and-forth a little at a time til it comes out. Just realize no matter what you do, you may have to deal with at least 1 broken bolt.
    David Teitelbaum

  7. #7
    Member
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    I've never had any luck with the cold sprays on 'really' stuck bolts. Maybe it works fine on stubborn bolts.

    Generally you need the bolt red hot. Whether it be from oxy-fuel or induction, that doesn't matter (I have an induction tool, but it's pretty cumbersome). As mentioned, propane takes so long (and won't ever get hot enough as far as I am concerned), you start heating other parts as you wait.

  8. #8
    Mad scientist DrWin's Avatar
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    Quote Originally Posted by SupercoolBill View Post
    Been breaking bolts left and right on my project. A buddy just gave me one of these to try. 20220121_071033.jpg

    Sent from my SM-G970U using Tapatalk
    Well, did you try it?
    Please excuse the crudity of this DeLorean as I didn't have time to repair it yet.
    VIN 10207 - December '81, Gray Interior, 3-speed automatic, stock PRV engine.

  9. #9
    Mad scientist DrWin's Avatar
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    Quote Originally Posted by 82DMC12 View Post
    I don't have any experience with cold sprays or induction. I'm curious about them though and would try them, given the opportunity.

    Most of my research seems to indicate that a mixture of 50/50 acetone and auto transmission fluid is a very good penetrating oil. There is also a spray called Aerokroil which is fairly expensive but seems to be known as the best retail spray there is. Hard to find but it's on Amazon. I bought some this year while doing a full front and rear chassis refurbishment and VOD project and so far I've been very happy with it. It was recommended to me by a mobile truck repair technician.

    https://www.amazon.com/Kano-Aerokroi...dp/B000F09CEA/

    I've also used MAP with a Bernzomatic TS8000 swirling burner and that works pretty well too. Acetylene is apparently "the best" but not easy for a Sunday shadetree guy to get a hold of in a pinch. Many hundreds of dollars in equipment just to get set up for something you will rarely use.

    So, for the regular guy wrenching, my suggestion is an oil can with 50/50 acetone + ATF, a can of Aerokroil, and a good quality MAP torch. But for real, patience is the main thing you need. Recognize which bolts are likely to be a problem and soak them for a couple days first. Spray them twice a day until GO TIME. Strike the bolt head squarely with a hammer every now and then to loosen them up. Hit the surrounding metal (NOT the bolt head) with some heat, and then try to turn them out. Best to use a 6-point socket and turn the bolt hard the first time. If you try to go slow, it's more likely to twist the metal so it breaks. Give it a good firm turn so it shocks loose. If it's still feeling tight, spray more penetrating oil and wait. Then turn it out maybe one full turn, then back in half a turn, and go back and forth between those two points with the ratchet until it's moving freely. Then go another half turn or full turn past that point. Stop, and turn it back into the hole, back and forth until it's loose. And keep coming out like that. Just a bit further each time.

    Get the bolt out, blow the hole out with compressed air, and replace the bolt if it's at all rusty or suspect. Oil the new bolt with cutting and tapping oil and run it in a couple times to make sure the threads are good and lubricated. That way you don't make things worse and you'll be less likely the crossthead when re-installing.

    If the threads are open on the other side, like for example the holes that you screw the sway bar into the front frame extension, spray both sides of the bolt. And that would be very easy to chase the threads out with a quality thread tap before re-installing. There is a special tap for blind threaded holes but I don't own any of those.
    Well - I do have som acetone standing around and also some ATF Dex II, so why don't I try that? Thanks for the tip. I suspect I'll try induction over open flame b/c I'm not really confident that I wont make more trouble that progress with an open flame in my (inexperienced) hands.
    Please excuse the crudity of this DeLorean as I didn't have time to repair it yet.
    VIN 10207 - December '81, Gray Interior, 3-speed automatic, stock PRV engine.

  10. #10
    Mad scientist DrWin's Avatar
    Join Date:  May 2020

    Location:  Denmark

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    Quote Originally Posted by David T View Post
    The reason the bolts break is that you have plated steel bolts in aluminum and eventually the plating on the bolts corrodes allowing the steel and aluminum to corrode together. Hard to know which bolts will break, some will come out easily and others will just twist right off. Even with precautions you can easily break bolts. My favorite method is an acetylene torch but you can't always use it because of combustibles nearly or heat sensitive materials. Sometimes sprays and liquids can be helpful but it is always hard to get them where they need to be. They seem to work better once you can get the bolt to move even if only a little. The best advice is when you take the bolts out, turn them back-and-forth a little at a time til it comes out. Just realize no matter what you do, you may have to deal with at least 1 broken bolt.
    I suppose you are right. I'll have to cross that bridge once I get there. Hopefully not this winter, but if that happens, I'll know where to ask about removing the sheared bolt(s).
    Please excuse the crudity of this DeLorean as I didn't have time to repair it yet.
    VIN 10207 - December '81, Gray Interior, 3-speed automatic, stock PRV engine.

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