I've got this problem, I've seen several threads with problems that were pretty similar...but none that are the same.

When I first start the car, the coolant light flashes on and off for 1 minute and beeps several times. After that 1 minute it's never on anymore.

While driving the car is fine, but when I'm idling at a stop light or anything to that effect the gauge rises up to about 3/4 of the way to max. When I start driving again, the temp gauge slowly moves its way back to 1/2 way. The A/C has little to no effect on whether it overheats or not.

When I shut off the car earlier I heard bubbling, and saw the coolant in the overfill was bubbling. I slowly opened it up to let it vent out. (not sure if I should of or not) So now the coolant level is at the bottom of the overfill reservoir.

The thermostat and coolant temp sensor were both changed about 2 years ago. Although I'd like to do the work myself now as the prices were pretty outrageous for that. If anyone can point me in the general direction for a diagram of an 01 TT so I could do the maintenance myself I'd greatly appreciate that as well.

Any help will be greatly appreciated!