Coolant Leak Audi A4 AFN: Causes & Fixes

Dear fellow enthusiasts,

My A4 has been experiencing a slight, intermittent coolant leak (pink stains in the garage ) for some time.
It was accompanied by increasingly frequent 'gurgling' sounds in the heating heat exchanger. Of course, instead of coolant, there was now air in the system. Bleeding the system provided a temporary improvement.
As described in the forum on several occasions, the engine was running dry after a longer and more demanding drive. The next morning, there were occasional instances of the infamous pink spots.
In my case, it was the O-ring on the temperature sensor, but I also replaced the flange at the same time.

Tip:
Since O-rings and hoses are difficult to install when dry, I use hot water grease from the sanitary area for this purpose. Applied in a very thin layer, the hoses slide easily over the connections.
Is there anything better, or are there any objections to using ???


The pictures speak for themselves.

'My Passat has been making a bubbling noise for 30,000 km now, and I'm also experiencing coolant loss. Perhaps the coolant is leaking out from the coolant temperature sensor, and it might not be the head gasket that's pushing exhaust gases into the cooling system.'