Overheating issue

I am aware this is common on these cars, a friend of mine has an 2009, he said it overheated, he got the dummy light so he stopped. He let it cool a bit and then drove, until he got home. Went to check it, no leaks, water is full, fan comes on for AC as well when engine temperature is at optimum. Checked with scanner, since these do not have a temperature gauge, coolant temperature and outlet are pretty close to each other, electric water pump rpm keeps fluctuating when driving, goes to zero all of a sudden and then a minute late goes back to average range, during that one minute the car overheats. Pretty much a water pump issue or is it supposed to fluctuate like this?