The bane of any car enthusiast is dealing with broken bolts. Once you notice a bolt broke off in the engine block, it’s best to remove it immediately. Otherwise, the broken bolt can weaken the functioning bolts by exposing them to excessive pressure since the functional bolt will be compensating for the broken bolt. Fortunately, there are methods you can apply to remove a broken bolt without damaging the threads or the engine block.
There are two effective techniques that you can apply depending on the bolt location and type of tools available to extract a broken bolt. First, you can use a bolt extractor to drill out the broken bolt, or weld a nut on the sheared-off bolt, and then screw out the bolt with a wrench.
Keep reading as we discuss broken bolt extraction tools and all the ways you can safely and effectively remove broken bolts from an engine block.
What is the best tool to remove a broken bolt?
The best tool to remove a broken bolt is a bolt extractor. Bolt extractors or easy-outs are hardened bits with tapered left-handed threads. Each bit has a square head that supports turning with an adjustable or flat wrench or fitting into a drill. Then the reverse threads on the bolt or stud extractor screw in counterclockwise into the broken bolt while the bolt backs out.
Additionally, the tapered shaft allows the extractor to fit tightly into the pilot hole on the head of the bolt or stud. So while turning the extractor counterclockwise with a drill or wrench, it digs into the broken bolt more while the bolt backs out. These bolt extractors come in a kit of varied sizes, so you can choose the best one depending on the bolt size.
There are two types of bolt extractors; cam-style and multiple-piece kits with a tool for all bolt sizes. The cam-style extractor is suitable if the broken bolt has enough diameter protruding for the extractor to grip. On the other hand, the fluted extractor is excellent if the bolt breaks too close to grab.
How do you drill out a broken bolt in an engine block?
There are two methods for extracting a broken bolt from an engine block. The first involves welding on the broken bolt. The second requires drilling the bolt out. The process and time it will take to remove the broken bolt depend on where you’re removing it from and the method you choose. Since one method won’t work in all situations, we have described the two ways to remove a broken stud from an engine.
Option 1: Drilling out a broken bolt
This method is the best for effectively removing a broken bolt from an aluminum engine block, as they are more prone to damage. With the proper tools, you can easily perform this task with basic drill operation skills. However, the challenge is you have to be careful not to break the extractor in the bolt. Since extractors are harder than most drill bits, getting the broken bolt out may be impossible.
Things you’ll need
- Bolt extractor set
- Penetrating oil like WD-40 for lubrication
- Left-handed drill
- Hammer
- Center punch
- Tap and die set
- Gloves
- Eye protection
- Magnet or compressed air
Directions
- Disconnect the car battery to prevent any risk of electrocution while working on the engine. Do this by removing the negative cable from the battery.
- Remove anything that could obstruct you from the broken bolt’s location. This includes disconnecting electrical cables that may get in the way of your process.
- Spray the penetrating oil generously around the area with the broken bolt and allow it to sit for more than 15 minutes. This allows the oil to penetrate the crevices around the broken bolt and help loosen it up.
- Wear safety glasses and gloves. Using the bolt extractor involves drilling and hammering, which can send shards of metal flying and potentially cause eye or skin injury.
- Take the center punch and hammer and make a center point on the bolt head. First, ensure the punch sits perfectly in the middle of the broken bolt head, then make one gentle tap with the hammer. A center punch is a tool that forms a dimple on metal surfaces to prevent the drill bit from slipping.
- Select an appropriate drilling bit size. A drill bit that is too small will require a smaller and weaker extractor with a higher chance of breaking, while a very large bit will damage the threads on the broken bolt.
- Activate the reverse setting on the left-handed drill, then position your drill bit into the center point and drill through to make a pilot hole. The left-handed drill is essential as its threaded in the opposite direction, similar to the broken bolt, thus preventing the bolt from getting tighter.
- Replace the drill bit with the extraction bit, insert it into the pilot hole, and then turn it clockwise into the pilot hole on the broken bolt until it’s snug.
- The extractor bit has a tapered opposite thread, so you will continue using the reverse drill setting until the broken stud pulls out. Then, to avoid breaking the extractor bit inside the bolt, drill out the broken bolt slowly and steadily until the entire bolt has been fully extracted.
- Alternatively, you can use a wrench or tap and die set to turn the extractor counterclockwise until it pulls out the broken bolt. This method is most suitable if you want to remove broken bolts in a tight space, as it’s a relatively slow process.
- Finally, clean off the metal shavings from the drilling and broken bolt using a magnet or compressed air, and install the new bolt. Then, reassemble the engine and reconnect the battery.
Note: It’s advisable to use high-quality drill bits such as those made of cobalt, as they are sharper and more durable. Low-quality drill bits will likely snap off and cause accidents or worsen the issue.
Option 2: Welding out a broken bolt
The main tool for this process is a MIG welder or a stick welder, depending on the broken bolt location( below, above, or flush with the cylinder). This process is relatively inexpensive but not always effective. Some engines have different metal types, which can be difficult to weld. The welding technique requires knowledge of metalworking, welding, and heat transfer. For instance, one ought to know that most turbocharged engines have titanium alloy bolts that can withstand a great deal of heat to fuse and more caution.
Things you’ll need
- MIG or TIG welder
- Wrench
- Flat washer
- Washer and nut( same size as the broken bolt)
- Welding protective gear
Directions
- Disconnect your car battery.
- Clean the broken bolt and its surrounding areas to ensure the weld holds. Also, clean the place you attach the positive/ grounding clamp when welding to ensure there’s no resistance to current flow. The broken bolt surface must also be clean for the welding to adhere.
- Ensure the washer or nut has the same inside diameter as the broken bolt so it can fit snugly to the bolt.
- Place the flat washer and the nut on top of the broken bolt.
- Then weld the inside of the nut to the broken top of the bolt.
- Use the wrench to extract the welded nut and broken bolt out of the engine block.
- Alternatively, you can avoid the washer-nut combination and construct the weld to create a custom-fitted bolt that is removable once above the surface of the head. However, you need to be cautious of the temperature to avoid burning the metal you’re working on.
- Before welding, you can tack the nut to the broken bolt first so that parts properly align before the final welding. Tacking refers to welding pieces of metal together through pressure and heat application.
- After welding the washer and nut to the broken bolt, allow it to cool down for a few minutes.
- Then use a wrench to unscrew the broken bolt from the engine.
Ideally, you should remove the broken bolt while keeping the threads intact. However, if you damage the threads on the engine block, you will have to repair it, which can be costly and time-consuming. So regardless of your method, ensure you keep the threaded hole intact.
How do you remove a bolt with the head snapped off?
Removing a stuck bolt with no head is similar to removing a broken bolt with a head. However, the only difference is if you use a fluted bolt extractor of the right size. Here’s the process for removing a seized bolt with no head:
- If the stuck bolt has left a shank with an uneven surface at the top, you must flatten it out before drilling it. Place a piece of paper over the engine block and make a hole over the broken bolt. Place some modeling clay under the paper around the bolt to make it hold. The paper will prevent filed metal chips from getting into the engine. Then file down the top section until it’s flat and even.
- Take a drill bit that corresponds to the extractor size you’ll be using.
- Apply some lubricant to help the drilling process and avoid overheating the bolt.
- Position the drill at the center of the broken bolt and drill into the broken bolt to the specified depth.
- Hammer the flute extractor into the hole. Then use a wrench to twist the bolt extractor counterclockwise until the bolt comes out.
Conclusion
Regardless of the reason for the broken bolt in your engine block, it’s important to know how to remove it to allow your engine to function properly. You can drill the bolt using a bolt extractor or weld a nut on the broken bolt and screw it out with a wrench. With patience, the right tools, and our detailed guide below, we hope you can remove broken bolts from an engine block without damage.