How to Drill out Broken Bolt in Engine Block

Breaking a bolt is one of the most frustrating things that can happen while working on an engine. A broken bolt stuck in the engine block can be a nightmare as it can cause severe damage if not handled correctly. However, with the right tools and techniques, you can drill out a broken bolt in an engine block easily and safely. This comprehensive guide will take you through the steps involved in how to drill out broken bolt in engine block.

How to Drill out Broken Bolt in Engine Block

Can You Drill out The Broken Bolt in The Engine Block?

Have you ever experienced a broken bolt stuck in the engine block? It can be a frustrating situation that requires a quick fix. Many car enthusiasts wonder if drilling out the bolt and solving the problem is possible. The answer is yes, but it requires the right tools and techniques. First, you need to identify the size and position of the broken bolt and select an appropriate drill bit.

Then, you should use controlled force to prevent further damage to the engine block. It’s crucial to work slowly and carefully to avoid any unwanted outcomes. Overall, drilling out a broken bolt is a feasible solution, but it requires skill and patience.

Why Should You Drill out A Broken Bolt in The Engine Block?

Broken bolts are a common issue in automobile repair, and it’s important to address them as soon as possible. While it may seem tempting to simply leave a broken bolt in the engine block, doing so can have serious consequences. Over time, the bolt will start to corrode and can weaken the integrity of the engine block. Removing a broken bolt can be a daunting task, but it’s one that is well worth the effort.

Broken Bolt in the Engine Block

By drilling out the bolt and replacing it with a new one, you’ll ensure that your engine stays in top shape for years to come. So if you’re faced with a broken bolt, don’t hesitate to take the necessary steps to fix it.

How to Drill out Broken Bolt in Engine Block – A Comprehensive Guide

Step 1: Preparation

Before you start drilling out a broken bolt, you must have the necessary tools and equipment. You will need a left-handed drill bit, a drill, a center punch, a hammer, a tap set, and some penetrating oil. Use penetrating oil to loosen the bolt if it’s stuck, and allow it to sit for a few minutes. Use a center punch and a hammer to create a small indentation in the center of the bolt. This will help to guide the drilling process.

Step 2: Drilling

Choose a drill bit of an appropriate size and start drilling the center of the bolt. Use left-handed drill bits because they are designed to turn counterclockwise, which can help to extract the bolt automatically. If the bolt doesn’t come out, drill a hole slightly smaller than the tap diameter. Increase the drill size gradually until you reach a size just below the diameter of the bolt.

Start Drilling the Center of the Bolt

Step 3: Tap and Extract

Once you have drilled a hole in the center of the bolt, use a tap set to create threads in the hole. Use the same thread size as the original bolt. Turn the tap counterclockwise to extract the bolt. If the bolt doesn’t come out, use a bolt extractor. Place the extractor into the hole and turn it counterclockwise with a wrench or pliers.

Step 4: Clean and Reassemble

When you have successfully removed the broken bolt, use a brush or compressed air to clean the debris from the hole. Check the threads and clean them as well. Install a new bolt with the same size, length, and thread pitch, ensuring that it is correctly tightened. Make sure everything is lined up and secure before finishing up.

Step 5: Prevent Future Breakages

To prevent future bolt breakages, consider the strength of the bolts you’re using, the torque settings, and the environmental conditions they are exposed to. Lubricate bolts to reduce friction, keep the torque set to the appropriate settings and ensure the bolts are environment-appropriate.

Step 6: Use Loctite

Loctite is a chemical thread-locking compound that helps to prevent bolts from loosening and breaking. Apply some Loctite to the threads of the bolt before installing it, and let it sit for a few minutes before tightening. This will help keep the bolt securely locked in place so that it won’t break.

Step 7: Seek Professional Assistance

If you find yourself in a situation where the bolt still won’t come out, it’s best to seek help from an experienced professional. A professional will be able to assess the situation and advise on how to safely remove the broken bolt without damaging other engine block components.

 If you need to drill out a broken bolt in your engine block, following these seven steps can help you do it safely and effectively. Having the right tools and equipment on hand, as well as patience and care, will ensure that the job is done correctly. As always, if in doubt, seek professional assistance.

5 Considerations Things When You Need to Drill Out Broken Bolt in Engine Block

1. The Type of Bit You Need

One of the most important things to consider when drilling out a broken bolt is the type of bit you need. Two main types of bits can be used for this purpose: an impact drill bit and a standard drill bit. Impact drill bits are designed to withstand the high-torque force of an impact drill, making them ideal for use on tougher materials like engine blocks. On the other hand, standard drill bits are not as durable and are more likely to break if used with an impact drill.

Main Types of Bits

2. The Size of the Bit

Another important consideration is the size of the bit. The size of the bit will determine the size of the hole that is drilled, so it is important to choose a size that is appropriate for the job at hand. If the hole is too small, it may not be large enough to accommodate the new bolt. However, if the hole is too large, there is a risk of damaging the surrounding area.

3. The Material You Are Drilling Into

The material you are drilling into is also an important consideration. Engine blocks are typically made from cast iron or aluminum, both of which are tough materials to drill through. If you are working with a softer material like wood, however, you may be able to get away with using a smaller bit.

4. The Speed of the Drill

Another thing to consider is the speed of the drill. When drilling through tough materials like engine blocks, it is important to use a slow speed not to overheat the bit and damage it. However, if you are working with a softer material, you can use a higher speed without damaging the bit.

5. The Direction You Are Drilling

Finally, you need to consider the direction you are drilling. When drilling out a broken bolt, it is important to drill in a straight line to not damage the surrounding area. If you start drilling at an angle, you risk breaking through into another area you didn’t intend to drill into.

Important to Drill in a Straight

Benefits of Drill out Broken Bolt in Engine Block

A broken bolt in your engine block can be a frustrating and overwhelming problem for any vehicle owner. However, drill-out broken bolt techniques have been developed to make this process easier and more efficient. Removing the bolt using these methods, it can help prevent any further damage to the engine block, thus prolonging the life of your vehicle.

Additionally, drill-out broken bolt techniques are cost-effective and can help save you money in the long run by avoiding costly repairs or replacements. It’s easy to see why more and more vehicle owners are turning to this solution when faced with a broken bolt issue.

Some Common Mistakes People Make When Trying to Drill Out Broken Bolt in Engine Block

Facing a broken bolt in your engine block is no fun, but attempting to drill it out can be even more frustrating if you’re not careful. Unfortunately, many people make the same mistakes when trying to remove broken bolts through drilling. One of the most common mistakes is not using the correct-sized drill bit, which can damage the threads surrounding the broken bolt.

Another mistake is not applying enough pressure, causing the drill bit to wander off-center and further damage the surrounding area. Lastly, a lack of patience can lead to attempting to remove the broken bolt too quickly, causing the extractor bit or easy-out tool to break off inside the bolt. While it can be tempting to rush the process, taking your time and using the proper tools and techniques can prevent even more costly repairs down the road.


Broken bolts can be a headache, but you can quickly remove them with the right tools, patience, and guidance. By following the steps highlighted in this comprehensive guide, you can effortlessly drill out a broken bolt in an engine block. But always be careful and take necessary precautions along the way. With a little practice, you’ll be a bolt-extracting pro. Thanks for reading our post about how to drill out broken bolt in engine block.

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Enrique Howard

Hi, I am Enrique. I started my professional life as a handyman and did a lot of external and internal repair of home and office with a little bit of electric and plumbing support. I have extensive experience in tools testing such as drilling, turning, milling, and non-conventional machining like EDM. So let me help you on your journey towards becoming an enlightened DIYer with amazing tools that you can use on your project.

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