2000 A6 2.7T overheating

[kf21857 at comcast.net]

No, there were no obvious signs of coolant loss so I think it occurred over a period of time prior to the overheating.  I agree that this is an issue that needs to be addressed and I will look for the leak while I have it apart but this thing went from normal to overheated in about 3 minutes so I am of the opinion that there was a mechanical failure of some kind and there are no blown hoses or anything else obvious.  I was doing about 60 when it happened so I don't suspect the cooling fan and the first thing I checked when I pulled over was the dipstick and there is no evidence of water in the oil.  I am betting it's a broken water pump, which apparently is not uncommon.  I will let you know what I find.  I was planning to tear it down to look at the timing belt anyhow.  Thanks for your help.
Dave
-------------- Original message -------------- 
From: Huw Powell <audi at humanspeakers.com> 

> 
> > 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. 
> 
> So, just for clarity all around, the couple of quarts was lost *during* 
> the overheating through the pressure cap? 
> 
> If so, let's see, it could be: 
> 
> *Tstat stuck closed - should be easy to replace? 
> *Water pump failed - would also kill pass. compartment heat, I think? 
> *Radiator fan/relay/fuse/sender failed - should be easy to test? 
> *Head gasket leak - might put some coolant in oil, can be tested for? 
> *System clogged somewhere - like WP, no heat should be a result? 
> 
> -- 
> Huw Powell 
> 
> http://www.humanspeakers.com/audi 
> 
> http://www.humanthoughts.org/