2000 A6 2.7T overheating

[urq]

I have no BTDT on your particular vehicle, but from years of Audi ownership
I'd say that your bit of skepticism is probably well taken.

That said, I think I'd be a bit less cavalier about finding the coolant
reservoir to be a half gallon low ... did you refill it when you noticed it
was low?  Based on your observations that the engine compartment didn't seem
hot and the fan was running on low, it may be that the coolant was low
enough to make the gauge temp sensor above the water level.  Some older cars
had the level sensor wired into the temp gauge so that the coolant low would
make the temp gauge go up and the overheat light flash ... I can't believe a
2000 model would have anything like this.  My recommendation, make sure the
coolant level is where it is supposed to be and repeat the test.  You
probably also want to try to find the leak ... another characteristic of
Audis is that they use plastic valves in the coolant path, and these valves
get brittle over time and can cause a very fast, catastrophic leak.
Happened on my 1978 Audi Fox, and pretty much every Audi I've owned since in
some form or another.  I think the worst one was the aux coolant pump on my
'88 5kCSQA ... happened while the wife was driving on the freeway, and I
suspect I very narrowly avoided a warped head.  I personally don't have a
high opinion of Wahler thermostats, but based on your description so far the
t-stat isn't a likely culprit.

Steve B
San José, CA (USA)

-----Original Message-----

I was on the freeway this afternoon when my 2000 A6 2.7T began overheating
rather abruptly.  I pulled off and let it cool for a few minutes until the
temp gauge dropped to a reasonable level, then made it to my destination,
which wasn't far.  I had to stop several times for the trip back home.  The
coolant level was down a couple of quarts but not extremely low.  No visible
leaks and the coolant level isn't dropping.  The cooling fan is running on
low speed but the engine compartment doesn't really feel that hot.  The car
has been running fine even on hot days so something failed suddenly.  Bad
temp sensor?  Stuck thermostat?  Internal failure in the water pump?  I am
thinking of temporarily replacing one of the coolant temp sensors with a
mechanical temp gauge before I start tearing things apart.  Any other
suggestions?