I remember the first time I had to tackle a stubborn flywheel. The service manual just said ‘remove flywheel bolts.’ Easy enough, right? Wrong. Hours later, knuckles bleeding, and cursing louder than a sailor on shore leave, I was still staring at those damn bolts. It got me thinking, and frankly, a bit desperate: can you use impact to remove flywheel bolts? It’s a question many DIY mechanics grapple with when faced with a seized fastener that laughs at a regular ratchet.
I’ve been wrenching on cars and bikes for longer than I care to admit, and I’ve seen my fair share of over-hyped tools and bad advice. Flywheel bolts are notorious for being torqued down to the heavens and often acting like they’re welded in place. So, let’s cut to the chase: can you just blast them out with an impact gun?
The Siren Song of the Impact Wrench
The allure of an impact wrench for flywheel bolts is undeniable. You’ve got this big, powerful tool that makes a satisfying racket and seems capable of anything.
The idea is simple: apply brute rotational force with rapid, percussive blows to break the bolt free. It feels like the nuclear option for a seized fastener, and in many cases, it can work. For many other bolts on a car – suspension components, exhaust clamps, crank pulleys – an impact wrench is often the fastest, easiest, and sometimes only practical way to get the job done without resorting to excessive heat or destructive methods. The sheer torque and hammering action can shock a bolt loose that a hand wrench simply can’t budge.
I’ve personally used my trusty air impact gun to zip off exhaust manifolds that looked like they’d fused with the heads, and it felt like magic.
However, flywheel bolts are a different beast. They hold one of the most important components in your engine’s drivetrain directly to the crankshaft. The forces involved are immense, and so is the torque applied during installation.
Manufacturers often use thread-locking compounds, and the sheer clamping force can basically ‘fuse’ the bolt into the crankshaft snout over time. This is where the power of an impact wrench can sometimes become a double-edged sword. While it provides the rotational force needed, the rapid hammering can, in certain situations, damage the threads in the crankshaft, especially if the bolt is already cross-threaded or if the impact driver is excessively powerful for the application. It’s a bit like trying to unscrew a delicate watch gear with a sledgehammer – brute force isn’t always the most elegant solution.
I recall one instance, working on an older Chevy V8, where the flywheel bolts were just being stubborn. I grabbed my mid-range electric impact wrench, figured it’d pop them right out. The first two came loose with a satisfying ‘thwack.’ The third one… well, it just spun. The impact wrench was just chewing up the bolt head. I had to stop, regroup, and resort to a breaker bar with some penetrating oil and a lot of patience. It taught me a valuable lesson: just because you can use an impact doesn’t always mean you should, or that it will work without complications. Sometimes, a slower, more controlled approach is better.
When Brute Force Might Actually Work
So, if you’re asking can you use impact to remove flywheel bolts, the honest answer is yes, you can try, and for many people, it works without a hitch. The key is understanding the type of impact wrench and the condition of the bolts. A high-torque, professional-grade pneumatic impact wrench with a good regulator can often be set to deliver controlled bursts of power, minimizing the risk of damage while maximizing the chance of breaking the bolt free. Electric impact wrenches, particularly the more powerful ones, can also be effective.
The percussive action is designed to shock the bolt loose, overcoming the static friction and any thread-locking compound that might be present. This is especially true for bolts that aren’t excessively rusted or seized. (See Also: Can You Use Wd40 To Loosen Bolts )
Think of it this way: the impact wrench applies torque in tiny, violent bursts. This rapid hammering action creates vibrations that can help break the bond between the bolt threads and the crankshaft threads, as well as any thread locker.
It’s more effective than a steady, continuous torque from a breaker bar because it basically ‘jolts’ the bolt free rather than just fighting against the static friction. For bolts that are torqued to spec and haven’t been subjected to extreme heat cycles or corrosion, an impact gun can be a godsend.
It’s the speed and the hammering action that makes the difference. The noise is a byproduct of this rapid hammering – a series of quick impacts that, when applied correctly, can do wonders.
I’ve found that consistency is also key. If you’re going to try an impact wrench, start with a medium setting and gradually increase if needed. Short, controlled bursts are generally better than holding the trigger down continuously. This gives you a chance to feel what the tool is doing and react if you feel the bolt head starting to round off or if the impact gun isn’t making any progress. It’s not about pure, raw power all the time, but about applying the right kind of force at the right time. For many common vehicles, especially those not subjected to harsh environments, this approach often proves successful, making the job much quicker than manual methods.
The Dark Side: When an Impact Wrench Bites Back
Now, let’s talk about where things can go south, and why many mechanics are hesitant to recommend using an impact wrench on flywheel bolts without reservations. The biggest risk is damaging the threads inside the crankshaft. Flywheel bolts typically thread directly into the crankshaft snout.
If the impact wrench is too powerful, or if you apply it for too long, or if the bolt is already slightly cross-threaded or damaged, you can easily strip those threads. This isn’t a cheap fix; it often means pulling the engine to repair or replace the crankshaft, or at the very least, having to tap new, larger threads, which can compromise the integrity of the crankshaft. I had a buddy who, in his haste, completely mangled the crankshaft threads on a Subaru WRX while trying to remove the flywheel.
He ended up having to source a used crankshaft, which was a nightmare and cost him a fortune in labor.
Another issue is bolt head damage. Flywheel bolts often have a specific head design, sometimes a unique bolt head shape or a very specific socket size. If your impact socket isn’t a perfect fit, or if the bolt head is already slightly rounded or corroded, the intense hammering action of an impact wrench can quickly turn a slightly damaged bolt head into a completely unusable, rounded-off mess. This makes it incredibly difficult, if not impossible, to get any grip on the bolt, even with a breaker bar or specialized bolt extractor. The speed at which it can round off a bolt head is frankly terrifying if you’re not careful.
There’s also the risk of snapping the bolt. While the goal is to break it free, sometimes the impact wrench can apply enough shock load to simply snap the bolt shank off, leaving the threaded portion still stuck in the crankshaft. This is arguably worse than a stripped thread because you now have a broken bolt to deal with, which is often much harder to extract than a seized but intact bolt. The vibration can also potentially loosen other fasteners in the vicinity, though this is less common with flywheel bolts themselves unless they’re extremely corroded or improperly installed. The common advice you’ll hear is to use a quality 6-point impact socket that fits snugly, and to use short bursts, but even with these precautions, the risk is still higher than with a controlled manual application. (See Also: Does Heating Rusted Bolts Help Get Them Free )
Alternatives and Best Practices
Given the potential pitfalls, it’s wise to have a plan B, or even a plan A that doesn’t involve an impact wrench initially. The tried-and-true method, often the safest for the crankshaft, involves a few key steps. First, clean the area around the bolts thoroughly. Then, apply a good quality penetrating oil liberally. Let it soak for a good while – sometimes hours, or even overnight if you have the time. The longer it soaks, the better chance it has of working its way into the threads and breaking down any rust or thread locker.
Next, use a high-quality, tight-fitting 6-point socket on a long breaker bar. Applying steady, firm pressure is important. You want to feel the bolt start to turn. If it’s extremely tight, try rocking it back and forth – tighten it a tiny bit, then loosen.
This back-and-forth motion can help break the static friction. If it still won’t budge, you can try applying heat. This is where things get a bit more involved and carry their own risks, but controlled heat can expand the crankshaft snout slightly, or break down thread locker. A propane torch is usually sufficient; avoid oxy-acetylene unless absolutely necessary and you know what you’re doing, as it’s easy to warp or melt components.
Always have a fire extinguisher handy.
If all else fails and you’re still stuck, then you might consider an impact wrench as a last resort. But even then, use it with extreme caution.
Use short bursts, on a lower setting if your tool allows, and listen carefully. If you don’t feel the bolt starting to turn or hear it give, stop. The key is to avoid excessive shock.
Some people even advocate for using a torque multiplier on a breaker bar, which provides significantly more torque with less effort and is a much more controlled application of force than an impact wrench. The consensus among seasoned mechanics is that while an impact wrench can work, it’s often not the best way, especially if you value the integrity of your crankshaft.
A Quick Comparison: Impact vs. Manual
Here’s a breakdown of how the two methods stack up, in my opinion:
| Method | Pros | Cons | Verdict |
|---|---|---|---|
| Impact Wrench | Fast, powerful, can break seized bolts loose quickly. | High risk of damaging crankshaft threads, can round off bolt heads, potential to snap bolts, noisy. | Use with extreme caution as a last resort, not a primary method. |
| Breaker Bar + Penetrating Oil + Heat (if needed) | Controlled force, much lower risk of damage to threads and bolt heads, quieter. | Can be time-consuming, requires significant physical effort, heat application carries its own risks. | The safest and most recommended method for most DIYers and professionals. |
The table above is pretty straightforward, but let me add some color. The ‘noise’ from an impact wrench isn’t just annoying; it’s a sign of the violent forces at play. You don’t get that with a breaker bar. You feel the resistance, you feel the bolt start to give, and you control it. With an impact wrench, it’s more of a gamble. You’re hoping the hammer blows do their job without causing collateral damage. I’ve seen too many good engines ruined by someone rushing the job with an overpowered impact gun. It’s the difference between a precision instrument and a blunt object. (See Also: Does Anti Seize Cause Bolts To Loosen )
Regarding the ‘People Also Ask’ questions I’ve seen floating around: For the question ‘What size socket for flywheel bolts?’, there isn’t a single universal answer. It varies wildly by make and model. Some use standard metric sizes (like 15mm or 17mm), others use imperial sizes, and some might even have oddball sizes or a Torx head. Always consult your vehicle’s service manual or look up the specific bolt size for your application before you start. A common mistake is assuming all flywheel bolts are the same size, which is a surefire way to end up with a rounded-off bolt head because you used the wrong socket.
What to Look for in an Impact Wrench (if You Must)
If, after weighing the risks, you decide to use an impact wrench, or if it’s the only tool you have readily available, there are a few things to consider to minimize potential damage. First, the type of impact wrench matters. Pneumatic (air-powered) wrenches often offer more control, especially when paired with a good regulator. You can fine-tune the air pressure to control the torque output and the intensity of the hammer blows. Electric and battery-powered impact wrenches have come a long way, but some can be overly aggressive. Look for models that offer multiple torque settings and variable speed triggers.
Second, the socket is important. You absolutely need a high-quality 6-point impact socket that fits the bolt head perfectly. Avoid 12-point sockets, as they are much more prone to slipping and rounding off bolt heads, especially under the hammering action of an impact wrench. Make sure the socket is in good condition – no cracks or worn edges. A snug fit is most important. If the socket is loose on the bolt head, stop immediately. Some mechanics even use a thin piece of shim stock or a bit of paper towel between the socket and the bolt head to make sure a tighter grip, though this is a bit of a hack and not always recommended.
Third, technique. As mentioned, short, controlled bursts are key. Don’t just hold the trigger down. Apply the impact for a second or two, release, then reapply if needed. Listen to the sound. A steady, rhythmic hammering is what you want. If it sounds strained, or if the bolt head starts to visibly deform, stop. You’re aiming to shock the bolt loose, not to pulverize it. Some higher-end impact guns have advanced features like torque control or auto-stop, which can be beneficial, but even with basic tools, controlled application is your best defense against damaging the crankshaft threads. Remember, the crankshaft is the heart of your engine; treat its threads with respect.
Faq: Flywheel Bolts and Impact Wrenches
Can an Impact Wrench Break a Flywheel Bolt?
Yes, an impact wrench can break a flywheel bolt, either by successfully loosening it or by snapping the bolt shank off. The percussive action can either shock the bolt free or, if the bolt is weakened or seized too severely, it can cause the bolt to fracture. This is one of the risks associated with using an impact wrench for this task.
Is It Safe to Use an Impact Gun on Flywheel Bolts?
It can be, but it’s not inherently safe and carries significant risks. The primary concern is damaging the threads in the crankshaft. If the impact gun is too powerful, applied for too long, or used on a bolt that’s already compromised, you can strip the threads. This is a much more serious and costly repair than dealing with a seized bolt.
What’s the Best Tool to Remove Flywheel Bolts?
The safest and most recommended tool is a high-quality 6-point socket on a long breaker bar, combined with patience and penetrating oil. If necessary, controlled heat can be applied. An impact wrench is generally considered a last resort due to the higher risk of damage.
How Do I Remove a Seized Flywheel Bolt?
Start with liberal application of a good penetrating oil and let it soak for an extended period (hours to overnight). Then, use a breaker bar with a snug-fitting 6-point socket and apply steady, firm pressure. If that doesn’t work, carefully controlled heat applied to the bolt boss or flywheel can help. As a final option, a carefully used impact wrench might break it loose, but proceed with extreme caution.
Final Thoughts
So, to circle back to the original question: can you use impact to remove flywheel bolts? The short answer is yes, you can, and sometimes it works just fine. My personal experience, and the experience of many mechanics I know, suggests it’s a high-risk, high-reward gamble. You might get lucky and zip them out in seconds, or you might end up with a stripped crankshaft or a snapped bolt, leading to a much bigger headache and repair bill. For me, the potential damage to the crankshaft threads just isn’t worth the slight time saving unless I’m absolutely desperate.
The safer, more controlled method with a breaker bar and penetrating oil is almost always the better route, especially if you’re not a seasoned pro who knows the feel of the tool and the materials intimately. It takes more patience, more effort, and more time, but it significantly reduces the chances of causing expensive damage. Think of it as an investment in the longevity of your engine components.
If you do decide to go the impact route, please, for the love of all that is mechanically sound, use short bursts, a quality 6-point socket, and know when to stop. Listen to your tool and your conscience. And always, always have a backup plan ready, because those flywheel bolts can be the most stubborn SOBs you’ll ever encounter.
