2000 A6 2.7T overheating

[Brett]

> I understand that, but the same symptoms occurred after refilling the
> expansion tank.  That is how I knew it was down 2 qt.  The system is
> definitely pressurizing.

A genie didn't wave a magic wand and have such a large volume of coolant
magically disappear.  You have a *substantial* leak.

Find and fix the leak, like everyone has been telling you.  You'll
probably find a cracked plastic piece, pinhole leak in a hose, or a loose
hose clamp that only starts to leak once the engine warms up and the
system begins to pressurize.  If you can't find a leak anywhere, you may
have a leaking head gasket.

Also, I don't know if the 2.7TT engine requires a specific purging, but if
you were down two quarts, you could have air trapped somewhere.  On the
older cars, the instructions were to park the car on a sharp incline and
run it with the cap off until the fan cycled on.  I have no idea what the
process is on newer cars, or even if it's necessary.  It's moot until you
figure out where the coolant is going, however.

Brett