Few things will make you feel worse than twisting the head off a bolt. It means the threads are seized in the hole, and now you have get the broken stump out of a tight spot. Having the right tools and know-how is essential to avoid that gut-punch feeling of breaking off hardware.
Picture this: your parts finally came in, it’s Friday night and you’re under the hood spinning wrenches. Everything is peachy until, wait, why isn’t this turning? You give it some more umph, and a little more. No dice. Now you give it all you’ve got and it turns, but a little too easy.
It turned all right, because you’ve turned the head right off the bolt. And now you’re screwed.
If you’ve done this once or twice, you already know that you want to avoid twisting the head off that bolt at all costs. Getting the bolt out without having to drill it out and tap new threads is always the better option.
6. Breaker bar
A lever is about the most simple machine there is. Using one of these babies is often times all you need to get that stubborn fastener free.
Breaker bars are pretty straight forward. You slip the appropriately-sized socket on the business end and it gives you a little more leverage than your average socket wrench. It has the added benefit of being simple. You can tap on it with a hammer without the risk of damaging any internal components.
5. Penetrating oil
This is a point of heated contention online. What’s the best? Which one works? “Brand A has blah blah blah, while brand B does whatever, and may God be merciful if you use WD-40 to loosen a nut because it’s technically not a lube or penetrant, yadda yadda yadda.” If you’re one of these types you can hash it out in the comment section below. First though, let me share what works for me.
There’s tons of information online about penetrants. Look through forums and you’ll read a bunch of posts by people who swear whatever stuff they’re using is hands down the best and only solution. There’s a whole galaxy of different offerings, from WD-40 to more exotic stuff. I have a handful of these in the garage and really can’t name a shining star among them.
When I broke off a cylinder head bolt on my flathead I tried all sorts of these oils and still the busted bolt just wouldn’t budge. I even tried a mixture of automatic transmission fluid and acetone that I read about. Which probably works, although I prefer something a little less flammable.
If you let the bolt soak and reapply penetrating oil as it seeps in around the threads you may be able to just turn it out. Sometimes if you try tightening it just a bit it will help break it loose before backing it out. But this takes time and what if the bolt remains stuck?
4. Impact Driver and a Bigger Hammer
Impact drivers work by turning slightly when they are struck with a hammer. Snap an impact socket onto the end and place that over the bolt and wail away with your hammer. If the bolt is rounded off, cut a slot with a saw or grinder in the head then use the slot screw bit.
I like drilling hammers because of the massive head relative to its length. The one I own came from Harbor Freight. It has a four pound head and a stumpy handle. It fits nicely into tight spaces and the heavy head means the hammer can do more of the work.
Some cars require impact drivers when doing their brake jobs. They come in handy if you have to break the screws loose on an old motorcycle case (I’m looking at you vintage Honda), or loosening striker screws when adjusting the doors of your old car.
3. A Torch
I’ve had good luck getting stuck hardware unstuck with what I call the heat and quench method. When it’s time to heat things up this is my go-to tool.
You can usually buy a torch at an auto parts or hardware store on the cheap. I recommend a trigger-start model rather than one that needs to be started with a striker, this way you can crank it up with one hand. This saves time, and saving time gets your bolt out faster.
I like to do a heat and quench method on hardware that’s really stuck. I heat up the bolt until it’s orange. Then I quench it with a penetrating oil that won’t erupt into flames. I’ve found that 3in1 oil serves this purpose. I heat the bolt, quench it and try loosening it again. I also clean up as I go with a wire brush.
This photo series shows the heating and quenching method used on a bolt stuck in my old car’s frame. Read more about it here.
This method isn’t always an option. For example, if there’s paint you want to preserve around the area or if the bolt is right next to your fuel line, you don’t what to use a torch. Any time you play with a torch, it’s a good idea to keep a fire extinguisher on hand. Keeping a torch among your tools pays off, not just for loosening hardware but for tons of other projects. I initially got mine to change the U-joints on a Blazer.
Sometimes even when you’ve done it all, that stupid bolt still snaps off. What then?
2. Thread Taps and a Tap ratchet
You’ve done everything you can but it still broke off. Relax, with the following tools you can handle this.
You will need a set of drill bits and some right-sized taps. That auto-punch from my previous article will come in handy here. Use it to punch the exact center of the remains of the bolt. Then, starting with a very small bit, drill a hole down through the center of the bolt being careful to remain parallel to the threads.
Then drill the hole out again with the next size up. Repeat the process until you have hollowed your bolt out completely. Do your best not to oversize the hole. Run a tap into the hole the same size as the hardware you wish to use. Tap sets don’t generally come with a tap ratchet, but it’s a good idea to get one. They’re inexpensive and save time.
Taps are made of hardened steel which allows them to cut new threads into just about anything softer, including cast iron, aluminum, plastic, etc. The trade-off for being so strong is that they are brittle.
Twisting a tap down in a hole is fine. Use some cutting oil and go slowly, backing the tap up occasionally to clear the threads and you’ll be fine. However, if you lean on the tap while it’s in the hole there’s a possibility of snapping it off.
Finally, and most importantly, use some patience. Usually when I twist the head off a bolt it’s because I’m trying to move too fast. I get irritated at how much time it’s costing me and think, “maybe I can give it just a little more muscle.” Nope. Broken.
I’ve learned to just take a breath and relax when I hit a snag. Make a plan to get it out and prepare myself for the time-consuming process ahead. Then, when it does come out in a timely fashion, and in one piece, I’m ecstatic.
Now you may be thinking, “Hey, who does this yahoo think he is? He didn’t even mention EZ-Outs or other types of bolt extractors. Clearly he’s an idiot who has never used any of these tools.” Actually, I have used these types of tools, but never with any success. In fact, when I tried using a name brand extractor on a stuck cylinder head bolt, I managed to break if off creating an even bigger mess.
I only suggest tools that I have used personally. If I can’t find exactly what I use online, I find something similar that I am comfortable recommending. Value is relative. If I buy a five dollar hammer that lasts me the rest of my life, what appreciable difference does the name brand product have? With tools, like everything else, you get what you pay for. These articles for the average DIY’er who may not have a garage full of fancy tools.
Two years ago Aaron Vick Starnes quit his well-paying bank job to pursue inevitable poverty as an automotive writer. He has experience in automotive restoration, and works at a shop restoring and customizing cars. Follow him on Twitter @AaronVStarnes and check out his blog.