I read some old post about valve clatter on a cold start...didn't seem to get resolved as to what the problem was. My '04 has started doing it...for one second or so...concerned about it hurting the engine.
Anyone know what is causing it??

 

Be sure you have 5w20 oil in the motor and its either blend of full synthetic.
and a MC oil filter.
What the issue is - oil pressure not up fast enough and or the oil filter is draining back and not holding pump prime.

 

I do use 5-20 blend but not a MC filter last time...that may be it.
Is it possible to change out the filter without draining the oil...or at least losing a bunch?
Or just wait till next o-change?

 

You can change it anytime.
It's way above the pan and only loses what is in the filter and what drains out of the top part of the motor area. Less than about a half quart.

 

A motorcraft or a Wix filter will resolve the problem. The Fram filters are crap if that is what you are using. I use a full synthetic oil, so run for about 3-4K miles, change the filter, and run for another 3-4K miles on the same oil, but with the added 1 quart to replace the oil lost in the filter change.