Knocking sound when idling - 1997 Toyota Corolla

If your engine is making the sound then eather the engine has been over reved and/or over heated and /or no oil changes. Its a sign that the engine will require a rebuild.Usually the noise is from a loose crankshaft or piston connecting rod bearing.Although taking the engine apart and checking it out is the only true way to find the problem.

Knocking? not ticking? drain your engine oil and drag a magnet through it. Look for metal that is gray or copper. Ouch, If you find anything, you have a rod bearing gone. It can be repaired if it hsn't hammered the rod or crand flat.