1. Attempting to Grip the Bolt:
* Extractors: These are specialized tools designed to grip stripped bolt heads. There are different types: screw extractors (spiral-type), bolt extractors (that grab the sides), and even ones that use a reverse drill bit. These are your best bet before resorting to more aggressive methods. Crucial: Use the correct size extractor for your bolt. A too-small extractor will likely strip it further. Lubricate the extractor well before applying force.
* Vice Grips/Locking Pliers: A last ditch effort *before* drilling, these can sometimes work if you can get a good grip on what remains of the bolt head. Be very careful not to round off the head further or damage the pulley.
2. Drilling and Extracting:
* Center Punch: Carefully center punch the center of the stripped bolt. This will give your drill bit a starting point to prevent it from wandering.
* Drill Bit: Use a left-hand drill bit slightly smaller than the bolt's diameter. A left-hand drill bit will actually work *with* the extractor. Slowly and carefully drill into the bolt. If you drill too fast or deep, you risk damaging the crankshaft.
* Extractor (again): Once you've drilled a pilot hole, use an appropriately sized screw extractor to remove the broken bolt.
3. More Aggressive (and Risky) Methods:
* Weld a Nut: If you have access to a welder (and are comfortable with welding), weld a nut onto the remaining bolt. Let it cool completely, then use a wrench to remove it. This carries a risk of damaging the pulley or crankshaft if done improperly.
* Drilling Out the Bolt Completely: As a last resort, you can drill the bolt all the way out. This requires precision and the correct size drill bit to completely remove the bolt without damaging the crankshaft. This will require a new bolt and potentially require re-tapping the threads.
Important Considerations:
* Pulley Removal: Before attempting any of these, you'll likely need to remove the crankshaft pulley itself. This usually requires a pulley puller tool. Using the wrong tool can easily damage the pulley or crankshaft.
* Crankshaft Damage: The crankshaft is a crucial engine component. If you damage it while removing the bolt, you'll have a much more serious problem.
* Professional Help: If you're not comfortable with these methods or lack the necessary tools, it's best to take your car to a qualified mechanic. The cost of repair will likely be far less than the cost of a damaged crankshaft.
* Penetrating Oil: Before attempting any of these methods, generously apply a penetrating oil (like PB Blaster) to the stripped bolt and let it soak for several hours, or even overnight. This can help loosen the bolt.
Remember safety first! Wear appropriate safety glasses and gloves. If you're unsure about any step, seek professional help. A damaged crankshaft is an expensive repair.
