3.0 DOHC Duratek Engine on a 2002 Sable with 125K on it: This loud rattle/tapping noise just started on our way home from Nevada last Saturday (9-7-14). It only makes the noise at a cold start-up for about 10-15 seconds (or until the oil begins to lubricate the valve train), then the engine is quiet. After the engine is warm, it doesn't make this noise at start-up anymore until the next "cold" start. This car has always had regular oil changes with full synthetic oil and I changed the oil just before we made this trip to Nevada (Kansas to Nevada and back again) and the oil level is full. Does anyone know what is causing this rattle/tapping noise? Any suggestions would be greatly appreciated. Thanks in advance.

 

This noise completely went away and I never did discover what caused it. The engine runs great now and is very quiet, even from cold starts. Has this happened to anyone else?