[davepl]

FWIW, I had a similar problem years ago and misdiagnosed it as the water pump when it was really the thermostat. You've done that twice, so its not your issue, but in case it helps anyone, the upper hose being hot does NOT mean that your thermostat is working properly.

I've never done it, but you should (when cold!) be able to disconnect the rad side of the upper rad hose, stick it in a bucket, and see flow when you start the motor. I'd pull the thermostat first so you don't have to mess with scalding fluids.

I'm not certain that would prove the pump to be ok (after all, maybe it only fails under pressure) but still should reveal a problem if its bad.

Is there a better way to test the water pump on the vehicle if it makes no noise and doesn't have an obvious bearing problem that gives it away?