I noticed something odd with my 2007 4.6 3V. Upon a cold start, I can hear some rattling. I use Motorcraft FL-820-S oil filters and 5W-20 synthetic engine oil.

I just recently changed the engine oil to fresh 5W-20 over the weekend, fired it up, and even pre-filled the filter beforehand. I still heard a rattling noise this morning.

Did the synthetic 5W-20 really bleed out of the hydraulic system this quickly? The engine runs very quiet and smooth. I only hear this rattling during a cold start and most of the time it is quite subtle. Is it the VCT system?

 

Mine also rattles with a cold start, and ONLY a cold start.

Unfortunately, pushing in the clutch seems to alleviate the problem. I hope it's not a throwout bearing going out or worse...

 

I hear the rattling regardless of the clutch position, although I generally hold the clutch during a cold start. I have found that it only occurs during a cold start. I can hear light "tapping" during hot idling but I suspect it is just the injectors/hydraulic lash adjusters like on my 00 Crown Vic's 4.6L 2V V8.

There's another source of rattling and I have isolated it to the gearbox. When hot idling in neutral, I will hear this rattling from the passenger compartment. Depressing the clutch makes it go away, releasing the clutch makes the sound come back.