When I filled it, I filled it through the drivers side radiator hose. Had the hose from the drivers side head off. Filled it til coolant came out of the head. So if it's air, I'm not sure how to tell or what to do.

Belt isn't slipping.

The wire from the sensor is all in loom, so I think it would be fine. Not saying there's 0 chance it's nicked somewhere along the line...just doesn't seem likely.