smithrd8003

At initial startup of a cold engine the temperature guage needle indicates "C" but the coolant temperature warning flashes red in the center display. Also at initial startup the high speed cooling fans immediately turn on and stay on. After running the car for as much as 20-30 min nothing changes: Temperature guage sits on "C", center dash indicates high coolant temperature and the fans stay on high. Feeling the resevoir tank with my hand it does get warm but not hot as I would expect in normal conditions.

The forums suggest
1) coolant sensor replacement (malfunctioning - $30USD cost and do it myself
2) thermostat stuck
3) air in the system.

The resevoir tank was replace 7 months ago and no problems until now. The new Audi Pink coolant 50/50 mixture in the resevoir at the normal level.

Outside temperature is 10 degrees Farenheit.

Recommendations?

Mister Bally

Replace defective $30 sensor or look ffor disconnected / broken wire.

smithrd8003

Great - Your suggestion is my intention - thanks loads and if it for some reasons turns out not to be the correct solution I'll let you know.

Thanks loads!

MP4.2+6.0

not an uncommon Audi problem as they get older. Other observations you made don't suggest any actual cooling system overheat type issue/malfunction.

mishar

1) Most likely that will fix your problem.

2) Not likely. Symptoms would be different. For the beginning, how could temperature gauge know that thermostat is stacked right at start?

3) Not likely. It would cause overheating and gauge would work.

ghibliss

Had the same problem with my car last Summer! It is not the thermostat or air in the system as neither one would prevent the water temperature from rising which is monitored by the sensor. Simply replace the sensor and when you install it do not tighten it completely until all of the coolant bubbles cease from coming out around the sensor. Then tighten it down completely and your system is bled completely of air and you are ready to go.

The fans which were in high speed cooling mode will now operate normally. The system is designed to run in high speed mode when the temperature sensor fails to prevent overheating.

smithrd8003

Sensor fixed it. Thanks to everyone!