Mellow drive (ok almost mellow) through the peninsula towards PCH1, barely 60F outside, temp gauge at the millimeter above 180, the fan kicked in and kept going, going and going, stopping for a sec then going again. Are there known problems with thermostats ?

I also discovered that the car makes a strange rattling sound when I pull from 1500 rpm in 5th or 6th, as if some metal plate was loose. Does that sound familiar ?

 

1500 RPM seems pretty low. Especially in the higher gears. I try not to go below 2200 or so.

The fan goes mostly after you park right?

 

No the odd thing is that it was while driving, could distinctly hear the whine, and for a long time.
1500rpm is low indeed, but that vibration/rattling noise does not sound orthodox at all, furtherless on a 16kmi car.

 

Does it sound like a high pitched whine when the fans come on while driving? I've been wondering that sound is at low RPMs while driving...

I know what they sound like when the car is parked.

 

I think the fans come on whenever the A/C compressor is running.

 

So for a few months now, my aux fan comes on systematically after I park my car in my garage. Mellow 25 minutes commute, mild temp.
Five to seven minutes after the car has been stopped, the fan goes on for 7 to 8 minutes then stops. Sometimes it does it again a second time after a few minutes. Thermostat was changed preventively, but without any effect.
My garage is slightly slopped so I tried to park the car with nose up and nose down, no change.
Is that normal ?

 

Yes normal.