Here's a breakdown of what to do:
1. Immediate Actions:
* Stop driving immediately: Continuing to drive with a knocking engine will likely cause irreversible damage.
* Turn off the engine: Don't let it run any longer than necessary.
2. Identifying the Source (Difficult without mechanical experience):
Engine knocking can stem from several sources. Pinpointing the exact cause requires mechanical knowledge and potentially diagnostic tools. However, you can try to narrow it down:
* When does it knock? Does it knock only when accelerating, decelerating, idling, or all the time? This helps determine the potential culprit.
* Loudness and location: Is the knock loud and consistent, or faint and intermittent? Try to determine if it seems to be coming from the top, bottom, or side of the engine.
Possible Causes (Requiring professional diagnosis):
* Rod knock: This is a very serious issue involving damage to connecting rods. It usually sounds like a rhythmic knocking that increases with engine speed. This often requires a rebuild or engine replacement.
* Main bearing knock: Similar to rod knock, but involves the bearings supporting the crankshaft. Also a serious issue.
* Piston slap: This is a less severe problem, often occurring when the engine is cold. It's a slapping sound rather than a sharp knock.
* Valvetrain issues: Worn or damaged lifters, rocker arms, or pushrods can cause knocking.
* Loose or worn timing components: Issues with the timing chain or belt can generate knocking sounds.
* Low oil pressure: Insufficient oil lubrication will lead to knocking. Check your oil level immediately (when the engine is cool!). Low oil pressure is an emergency and could indicate a serious problem.
3. Next Steps:
* Check your oil level and condition: With the engine cool, check the oil dipstick. Is the oil level low? Is the oil dirty, milky (indicating coolant contamination), or metallic (indicating metal shavings)?
* Have it towed to a qualified mechanic: This is crucial. Do not attempt to diagnose or repair this yourself unless you have extensive mechanical experience. A mechanic can properly diagnose the cause of the knocking and advise on the necessary repairs.
* Get multiple quotes: Obtain repair estimates from several reputable mechanics before proceeding with any repairs.
Cost Considerations:
Repairs for engine knocks can range from relatively inexpensive (if it's a minor valvetrain issue) to extremely costly (if it's a rod or main bearing knock requiring a rebuild or replacement engine). Be prepared for a significant expense, especially given the age of the vehicle.
In short: A knocking engine is a serious problem. Don't drive the car, check the oil, and get it to a mechanic immediately for diagnosis and repair.
