What is this awful noise?
 

I drove my car home Saturday night and noticed an odd noise while backing in the garage. It was late and I didn't think much about it. Then I went to drive it this morning and the noise was very distinct. I hear a slight belt squeal which I'm not worried about but the knocking noise is the concern. If I rev the motor I don't hear it until the rpms slow down again. Check out the following video taken from under the car passenger side:

What is this noise uploaded 6-18-2012 - YouTube

sounds like a loose spark plug. easy enough to check and yes they do come loose. pull off the coil packs and check each plug for tightness and if you have over 60 k on the car you might as well change them.

Remove the S belt and see if it goes away ?

I removed the serpentine belt and the noise went away. Slipped the belt back on the noise came back. I'm guessing water pump?

Wiggle the water pump pulley, if there is any play it is bad,. Also rotate it and if there is any roughness its, bad.

There is a small amount of play but seems to turn just fine. I'll start with taking it off for inspection. I'm at 78K so it sounds like motor mount maybe another item to look at replacing while I'm doing this? Any other suggestions for maintenance items while I have it taken apart?


Update 10:45 PM
After removal of the water pump it was obvious it had failed. I'll be ordering a new one shortly.

Thanks to all for you help on this one!