Greetings,

I have a 2001 Mercury Sable with 155,000 miles. The few days or so, I've noticed when I start the car, I hear this knocking noise under the hood...can't quite figure out where its coming from however seems like its coming from the back of the engine ...Once the car warms up and I drive it for about 15 minutes, the rattle sounds goes away and I don't hear it again until I cold start it the next day. Anyone know or have an idea what's the origin of the sound?

I am due for an oil change and I will get one tomorrow. I was told, maybe I have metals in my filter possibly.

Thanks,
Jay