2000 A6 2.7T overheating

[kf21857 at comcast.net]

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.

 -------------- Original message ----------------------
From: Brett Dikeman <quattro at frank.mercea.net>
> 
> On Jun 5, 2008, at 7:24 AM, kf21857 at comcast.net wrote:
> 
> > I appreciate the suggestion but the symptom I am describing is  
> > caused by the complete failure of something,  i.e. a stuck  
> > thermostat, not a small leak.  In another car I might suspect a  
> > broken fan belt but that isn't the problem here.
> 
> The cooling system is designed to run at a proper level, not "down a  
> couple of quarts", and if it cannot pressurize, the coolant will be  
> more likely to boil.  If you have a cracked hose or plastic fitting  
> somewhere, the system will also end up with some air in it, and that  
> will cause problems as well.
> 
> You should be able to confirm what's going on using any ODB-2 scan  
> tool to see what the ECU thinks the temperature is, since they're  
> probably different sensors.
> 
> Brett