How to Remove Rusty Bolts

how to remove rusty bolts


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


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,


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36 Responses to “How to Remove Rusty Bolts”

  1. Bill Butkus

    WD 40- stands for water displacement not a lubricant! The 40 stands for the different formulas , till they got it on the 40th try!

  2. Donald Wagner

    Kano Kroil the best!! Might take several applications over a couple of days.

  3. Screaming Goat Garage

    I have had good success with the ATF/Acetone mix but it eats through the seals in every pump oil can almost instantly. What do you use to dispense it from?

  4. Syd Coomes

    I found this interesting when you compared the various penetrating oils. When l haven’t been able to use heat, l have with some success cracked the nut by putting a hammer on one face and hitting the opposite face with a hammer which sometimes cracks the nut. Another method is to try and tighten the nut which can also crack the nut.This method works well on Phillips headed screws, clean out all the paint and muck out of the head, use screw locker in the head tighten and the loosen. This method is well known in the air line maintenance.


    I have found that if you try to remove the bolt while it is still hot, you can ruin the threads on the bolt.

  6. Ben Holsinger

    I've always had good results with heat and water. Heat the bolt cherry red and then quench it with water. The sudden change in temp and the different coefficients of expansion between the bolt and nut causes the threads to loosen up.

  7. Greg

    sometimes the quickest and easiest is to use an angle grinder with a thin cutoff wheel. Cut the bolt head or nut off and drive the remaining part thorough the hole

  8. Randy Hicks

    re: 40-year-old Jeep Cherokee bumper bolts (probably never removed before) I tried several liquid products to no avail - forget them! Go to HEAT. I was lucky with only the use of a 1500-watt heat gun and a lot of "manpower"... plus a cheater bar and BIG hammer!!!

  9. Paul

    Mark, there is a third and much better option. It is to use hydrochloric acid for the most rusted ones. After letting it sit for a couple hours, rinse off with water. This produces flash rust which can be removed with sulfuric acid. Then fush with water again ND it chemically changes the flash Rust to ferris phosphate (a white powder). Brush it off and it is ready for primer and paint. The chemicals won't work if you used wd49 or any oil before trying the acid as the acid will bead on top of the oil.

  10. Paul

    Thank you for the info.