on an 2001 a4 quattro 1.8t does the waterpump run off the timing belt, and does 750 sound like a decent price to be fully replaced?

 

750 with the timing and everything done is good

 

does the water pump run off the timing belt?

 

Yes it does.

 

2001 is AWM, which integrates the water pump drive to the timing belt. Make sure they are replacing the serp belts, tensioners, and rollers. $750 is straight-up cheap. Make sure they are using genuine parts and there is a warranty.

 

what about on a 2000 or below 1.8t?

 

What about it?

There was a split mid-year 2000, if I recall correctly. AUG and AWM are TB driven, anything earlier is serp-belt driven. Look in the engine bay; you'll see an extra serp belt driving the water pump.