How to Remove Rusty Bolts

how to remove rusty bolts

Q.

I am having a tough time removing rusted bolts on a total restoration project. Can someone offer a lead on removing them? Thanks!

A.

This is a question every car enthusiast has asked themselves. “What is the best way to remove rusty bolts?”

Basically there are two tried-and-true methods for unbolting rusty fasteners: penetrating oils and heat. Let’s discuss penetrating oils first.

Many enthusiasts quickly grab a can of WD-40, hose down the bolt, then try to turn it two minutes later, usually without success. Remember, those bolts have had 30+ years to rust together. Releasing them is seldom that easy.

In a published article in Machinist Workshop Magazine, they tested some commercially available penetrating oils on a group of nuts and bolts they had scientifically rusted to a uniform degree in a saltwater solution.

The fasteners were treated with a variety of commercially available penetrants, and the measured torque required to loosen them was recorded.

The breakout torque required for:

  • Nothing = 516 ft. lbs.
  • WD-40 = 238 ft. lbs.
  • PB Blaster = 214 ft. lbs.
  • Liquid Wrench = 127 ft. lbs.
  • Kano Kroil = 106 ft. lbs.
  • 50/50 blend of ATF and Acetone = 50 ft. lbs.

As you can see by the results of their test, the homebrew concoction of automatic transmission fluid and acetone worked best. But also keep in mind that acetone is very flammable and must be dispensed from a sealed metal container, similar to the old oil squirt cans. From my own experience, this solution works very well and seems to work a little better if you use synthetic ATF. I have also used Kroil for years, and because it’s less volatile than the homebrew, it is often my first choice.

Don’t rush it. When I have several bolts to remove that I know are going to give me trouble, I will often spray them down several times over the course of a couple of weeks before even trying to turn them.

If all else fails, I use heat—and I mean red hot! Simply getting a bolt hot with propane or gas seldom does the trick. It’s time to break out the oxy/acetylene torch and heat up the nut so it expands away from the bolt. Then, before it cools, wrench it off. Of course, if it’s close to anything that could combust (i.e. gas tanks, fiberglass bodies, etc.), don’t try it! Instead, spray on more penetrating oil and try again later.

There is another method to supply the heat directly to the bolt without affecting the surrounding area, and that is using inductive heating. While relatively new on the market, the inductive heaters get the job done with a lot less risk than using an open flame. However, their $500-$600 price point will put it out of range for many hobbyists.

Cautionary notes: Always wear eye protection when working with solvents. Penetrating oils contain solvents, so it is a good practice to wear rubber gloves to protect yourself from them. Always use acetone in a well-ventilated area as it is highly volatile. Never combine the use of penetrating oils and heat, as the fumes can be hazardous to your health. When using a torch to heat bolts, be aware of any other flammable components nearby and have a fire extinguisher ready.

I hope this helps, and if all else fails, check out this great video to see Brent demonstrate how to remove broken bolts using an easy out.

Wrench safe,

Mark

Reply to Joe Dial
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28 Responses to “How to Remove Rusty Bolts”
  1. Dennis Newman
    Dennis Newman

    Hi Mark, I used the ATF/Acetone on a 1930 Hercules engine, in an Ahrens Fox fire truck, that had frozen, Head cracked, and sat for 40+ years. I poured the mixture into the spark plug holes until it came out the exhaust and all other openings, let it set for a few months. All parts came out without damage no broken rings or pistons or bolts. The cylinder head was stitched, not welded. The engine now runs great. So the home brew works!

    Reply
  2. Buzz Madsen
    Buzz Madsen

    I have a ’65 year old Studebaker pick up on which I’m trying to preserve the original patina, even though it’s mostly down to the original primer and surface rust. I had bolts holding on the tail gate and I needed heat to get them off. I packed modeling clay around the area where heat from my torch would be applied. Also protected the surface around the bolt as much as possible with a cut and spread piece of conduit. Heated the nut red hot and it came right off without any trace of burning on the surrounding metal.

    Reply
  3. Rob Hilton
    Rob Hilton

    SeaFoam Deep Creep penetrating oil works really well and is relatively safe & inexpensive at around $8. Have used it on old engines that have sat out in the weather for years. It is in a spray can so easy to get into those hard to reach places. Rob

    Reply
  4. Don
    Don

    A old timer told me away to get some rusty lifter/ valve guides out of a old ford flair head v8 . Take a can of coke and pour it on the bolts .let it sit over night. I though this was a joke. But I did try it, guess what, they can out like butter. If Coke can do that, what does it your insides. This old trick might help.

    Reply
    • Customer Service Techs
      Customer Service Techs

      All of the tests I have read or heard of, use a 50/50 mix of ATF to Acetone. I have always used the same equal part ratio in my own shop with great results. Would a different ratio work better? Perhaps. But in my mind it would be hard to improve on the results the 50/50 mix delivers already. The only variable that many claim works better is to use synthetic ATF (because of its smaller molecule size). While I have tried both, they seem to work about the same in my own unscientific tests.

      Wrench Safe, Mark

      Reply
  5. Kevin Gill
    Kevin Gill

    on bolts that I can heat with a torch I get them red hot, melt a bit of candle wax on them and go drink a cup of coffee. works 99% of the time

    Reply
  6. Keith Florence
    Keith Florence

    I am into doing restos on early model Holdens Hq to wb and a vh commodore but do not have a credit card any more for these things

    Reply
    • Customer Service Techs
      Customer Service Techs

      Hello Keith, if you are inquiry about having a credit card to pay for the Premium Membership, we do except prepaid visa gift card as well. If you have any further question, please contact Customer Service at 1-855-706-3534. Thank you!

      Reply
    • Customer Service Techs
      Customer Service Techs

      Hello Keith, if you are inquiry about having a credit card to register for the Premium Membership then we want to let you know that you may also register with a prepaid visa gift card too. If you have any question, please contact Customer Service at 1-855-706-3534. Thank you!

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  7. larry schram
    larry schram

    I’ve had pretty good success with diesel fuel for throttle cables and engine blocks that were seized.somtimes it takes awhile but it works.thanks for the other tips.

    Reply
  8. Jeff isaak
    Jeff isaak

    Product called tri flow is the best that I have ever seen for anything rusty even smells like the old gun cleaning solvent they would sell ya

    Reply
  9. Charles
    Charles

    I was surprised at how well Liquid Wrench worked. Most younger people think the latest stuff has to be better and since LW has been around 100 years you don’t see it used much anymore. I mixed a batch of the Acetone and ATF, but haven’t had occasion to try it yet. One thing I noticed is it separates fairly quickly which means you have to remember to shake it before each use. Anyone else experience this?

    Reply
  10. Patrick
    Patrick

    I’ve been rebuilding starters, alternators and dc service motors (plows, salt water marine,etc.) for 33 years up here in the Northeast ( New England ). My biggest nightmare is a #12 screw broken off in an aluminum housing (dis-similar metals). I’ve tried many products, but keep coming back to Zep Q45 penetrant and heat. However, the ATF/Acetone suggestion has peaked my interest. I’ll be trying it out this coming week.

    Reply
  11. Joe Dial
    Joe Dial

    The best penetrating oil I have ever used is GM Heat Valve Lubricant. It will break rusty bolts better than anything else

    Reply
  12. Diesel DAN
    Diesel DAN

    Yes I can personally attest that the ATF works for rusty bolts and a product called Kroll is a close second too !! but hey heres a neet trick I bet not too many have tried !! and ive had some success with it , everyone uses heat as a last resort because it melts everything around it !! well try using a TIG torch for your heat source !! it gets the job done and doesn’t melt everything around it !!

    Reply
  13. Gary
    Gary

    When and if I have to heat a bolt etc I use a small welding tip with my oxy/acetylene I can use a low small hot flame to heat it up and not burn or heat other areas just takes a little longer to heat but not much longer.

    Reply
  14. kenneth
    kenneth

    Another thing to try after letting that rusty bolt soak is a sharp tap on the bolt or stud with a hammer. Use a punch if needed to get to the end of the bolt. Do be careful – don’t round off the threaded end the bolt.

    Reply
  15. John
    John

    I have used a product called KANO from Kano labs. It has never failed when I have the patience to let it seep into the rusted area. I think you can do a search on the web and you will find them. Good luck!

    Reply
  16. Paul
    Paul

    Ok but what’s a good approach to removing rusted bolts where only the head of the bolt is accessible?

    Reply
    • Customer Service
      Customer Service

      Hi Paul,

      It’s a common situation! Lots of penetrating oils and time to start…
      6-point sockets can keep you from ruining the bolt heads,
      If that fails, use heat. It’s best to heat the area around the bolt … we’re talking cherry red heat, not just hot.
      Some claim you can also heat the bolt really warm, but not too hot and apply penetrating oil as it will aid in drawing the oil in. (Too hot and the oil could flash)

      Hope this helps,

      Mark
      Classic Car Restoration Club Video Membership

      Reply
  17. John Michael Kent
    John Michael Kent

    You missed one very good and safe method. A nut splitter. They can be found at any auto parts store.

    Reply
  18. Patrick Ahern
    Patrick Ahern

    I a previous life I worked as a logger. When the weather was bad I would help the equipment mechanic repair and maintain the heavy equipment.
    He showed me a trick he used for hard to remove fasteners.
    Take a punch to the problem bolt and rap it hard with a heavy hammer. This will often loosen the rust.

    Reply
  19. Milt H Heger
    Milt H Heger

    Kroil is great and now there’s SiliKroil which ‘they’ say will enter a space 1 millionth of an inch!

    Reply
  20. Al Robinson
    Al Robinson

    I’m a Professional Licensed Mechanic from Ontario Canada where they spray the roads with salt in the winter to melt the ice. It works great but causes a nightmare with seized threaded products. Ontario is one of the worst provinces for this. I have tried many things over the years. My findings have been Krown Rust Control in spray cans allowed a good soaking time & a few applications followed by a few carefully aimed blows from a hammer to jar everything loose. If that fails oxy/acet heat to red hot seldom fails. With sensitive materials around it a well water soaked rag which is kept soaked protects them. Have fun.

    Reply
  21. Charles Woznak
    Charles Woznak

    Oil of wintergreen (It is a food flavoring and used as a topical rub for sour muscles.) applied to the rusted threads and allowed to soak in has worked for me when many other things have failed. It only takes a couple of drops. Smells good too. Think of a wintergreen lifesaver.

    Reply
  22. Tony
    Tony

    I have also used heat and melted a candle. The wax travels toward the heat and acts as a lubricant. This works especially well on brake bleeders.

    Reply