I'm pretty sure that I have a t-stat that is stuck open on my 1.8T.<p>1. Temp needle never gets to middle position.<br>2. Marginal heat<br>3. Drove 16 miles at 65mph and never got the temp needle above the 2nd tick from cold on the temp gauge.<p>On a non closed system it is easy to diagnose. Cold motor, open radiator cap, see if the coolant is circulating as soon as the engine is started. No such way on the A4. Does anyone know the proscribed service to determine this?<p>Thanks and regards,<br> Tim C.

I haven't checked my A4 yet, but if it's similar to my VW Rabbit, it has a return line that runs back to the plastic fill jug. You can see the water circulating there. I don't know if you checked that already or not.<p>G. Hale<br>'98.5 2.8 QMS

Not sure about the A4 (just havn't looked) but my older Audis had only one tube to the bottom of the tank and you couldn't see any circulation. The way I would tell is the top line (to the radiator) stays cold until the thermostat opens up, but if were stuck open it would warm up as the engine warms up.