Hi, Ive had the same issue, but I replaced the waterpump as the bearing war wearing and it had a lot of wobble, but wasn't leaking, and the alternator, as it was red hot, too hot to touch, when the block and hoses were not warm.I have the same issue. When engine is warm I hear it louder and only on low rpm. After checking every part with automotive stethoscope I found that the problem in water pump. Bought a new one from amazon and will let you know if it fixed after changing it. If is a water pump - driving can be dangerous with risk of motor overheating.
Still have the rattle. It seems to be the air con compressor and or clutch. Definitely more noise with air con on, and in gear, less in park. Not sure why, torque could alter some geometry slightly.
Got a new compressor drier and exspansion valve to fit next.
I think its something internal in the compressor is loose.
All parts new from Rockauto, only about 7 days to get to Australia !