Yea I don't think the water pump can really make any pressure that would make any difference. The pressure is make by the temp change in the water. That is why if you remove the rad cap on a hot motor, remove it by bleeding off the pressure and then reinstalling the cap on the hot coolant it will never make pressure again till it cools down and heated up again. I have a BB water pump on my parts washer and it works great but it does not make any pressure, it just moves the solvent.
