I am about to embark on the task of changing the thermostat on the i6 using the great post - https://www.freel2.com/forum/topic32245.html

I have read a number of posts about this task, can anyone advise on the easiest way to drain the coolant, having removed the under-tray and peering towards the base of the radiator it looks a real sod to remove anything related to cooling pipes,

thanks

Too late probably, but when I changed the coolant on my i6, there are two small twisting tabs, one underneath the car, near the bottom left corner of the radiator, and one on the front of the engine, on the middle of a coolant tube horizontally.
They just twist and open and drain. I let it on max heat on the buttons in the cabin.

It's on page 917 or thereabout in the servicemanual.

Kind regards,
Redfox