Hi performance cars do it to gain hp.  Gains in HP can be equated to
gains in efficiency and hence better mileage.
  One could replace the alternator with a generator and belt it to the
water pump. Then you could "motor" the generator to turn the water pump.
   An electric clutch, such as used on the A/C compressor, could be used
to connect them to the engine when the generator is needed to produce
current.
   Ken Lewis
   http://neksiwel.20m.com/

On Sun, February 17, 2008 9:54 pm, Wesley Pegden wrote:
> Something I've wondered about which is a little bit related to this is
> running the water pump off a small electric motor rather than a belt.
>
> The advantage, in my mind, is that you could have a decent rate of flow
> even when the vanagon is at idle, to cut down on coolant system stress
> when your stuck in traffic in the summer heat.
>
> I'm not sure what the impact would be on gas mileage.
>
> -Wes