1. Attempt to Start the Engine:
* Cranking: Try starting the engine. If the engine *doesn't crank at all* (the starter motor doesn't even engage), this is a strong indication of a locked engine. A dead battery will also prevent cranking, so check that first using a multimeter or jump-starting.
* Slow Cranking: If the engine cranks very slowly, it could also indicate a locked-up engine, though it could also be due to a weak battery, a faulty starter motor, or other electrical issues. Listen carefully for unusual sounds (more on that below).
2. Listen for Sounds:
A locked-up engine will usually make specific sounds while attempting to start:
* No sound at all (except perhaps the starter motor clicking): This is a key indicator. The engine isn't even trying to turn over.
* Grinding or scraping sounds: This suggests metal-on-metal contact, indicating something is severely damaged and seizing. This is a very bad sign.
* A "clunk" sound: This could be a connecting rod or other internal component that has broken or is out of place.
3. Check the Engine's Physical Condition:
* Attempt to turn the engine over by hand (if possible): On some vehicles, you might be able to access the crankshaft pulley with a wrench or socket. Try turning the engine by hand. If it resists turning or requires significant force, the engine is likely locked up. Caution: This should only be attempted by someone knowledgeable about engines and with proper tools. Incorrectly attempting this can cause injury.
* Inspect for any obvious damage: Look for any signs of leaks, broken parts, or unusual damage around the engine. This visual inspection can't diagnose a locked engine, but it can provide clues.
4. Consider the Circumstances:
* Recent overheating: An overheated engine is more likely to suffer damage that leads to a locked engine.
* Low oil pressure: Running an engine with low oil pressure can cause catastrophic damage resulting in a locked engine.
* Recent mechanical work: If you've recently had work done on the engine, it's possible something wasn't assembled correctly.
What to Do If You Suspect a Locked Engine:
* Do not attempt to start the engine further. Continuing to crank a locked engine will likely cause further and more costly damage.
* Have the vehicle towed to a qualified mechanic. A locked engine requires professional diagnosis and repair. It's a major mechanical issue, and attempting a DIY fix is likely to worsen the situation.
In short, a lack of cranking, unusual grinding noises, and resistance to turning the engine by hand are all strong indicators of a locked engine. This is a significant problem that requires professional attention. Don't try to diagnose and fix it yourself—get it towed to a mechanic.
