My daughter's 2002 Chevy S10 was running occasionally warm and I was going to get it checked out. I had just bought her new tires and she took it in to get it aligned. They said that her water pump had a leak. I've changed out many of those so I did it myself. It went smooth and uneventful, I also changed the thermostat and replaced the hose from the radiator to the reservoir tank (it was clogged and brittle) and got a new radiator cap while I was in there. Filled it up when I was done and have purged out air by idling it with the radiator, bouncing on the bumper and squeezing the upper and lower hoses. Getting some tiny bubbles still, but not like the big ones I got in the beginning. I can't turn on the heater to help with this because her heater core went out a while back and I bypassed it .(don't need a heater in AZ really )I've purged bubbles several different times now, and it is still warming up to the line over the middle (220),after about 4 miles rather than how it was running before, which was one line under the middle (200, the middle is 210). I keep purging and driving and this is still happening. I am not losing a drop of coolant from anywhere, the levels are maintaining fine. I'm not giving it back to my daughter until I can keep the temperature maintains lower than it is. I can see the thermostat is opening around 195, while idling with the cap off, right at 195 I can see it drop down everytime. Her oil was just changed and looks good. Any idea's????