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Water pump - O.E.M. or aftermaket?

In message <199610092029.QAA17882@coimbra.ans.net> "Sheffield Corey" writes:

> did my T-belt this summer and put in a GRAF pump that appeared to
> have a slightly larger impeller blade than what I took out, and I think the
> car does cool a bit better.

A bit "more" perhaps, but is it "better"?

All engines are designed to run hot.  For any given engine, there's a specific 
value.  You'll find the value for each engine given on the thermostat - 
typically on Audi engines it's 87 Celcius.  Any cooler, and you run the rick of 
increased wear.  The pistons, for example, are oval when cold and only become 
round at operating temperature.  The trick in providing cooling capacity is to 
handle high ambients and high engine workloads - the water pump in all Audis is 
more than capable of handling worst case loads, but the radiators and fans 
thereto may have a bit more work to do. 

 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club