1998 Chevy Cavalier Car Running Hot

I just recently had a crank shaft position sensor replaced on my car and after picking it up and driving it, it started to run hot. The water pump appears fine, doesn't seem to be a head gasket, but the fan doesn't appear to be working properly. I replaced the thermostat with a new fail proof thermostat. Burped out all of the air from what I could tell and for a while it ran good and then started running hot again. I did a flush on the coolant system and again it ran fine for a little bit and then ran hot again. The coolant that I flushed out didn't appear very nasty, therefor not sure if something is lodged within radiator, or if it is a fan issue. The fan has voltage and the relay is new. The fan comes on when you run the AC, but not sure that it's coming on when car heats up on its own. I have a new sensor to replace on the fan, but if it's getting voltage is it the sensor or a motor problem with the fan, or do I need a new radiator completely? Please help, this is turning into a nightmare.I mean nearly all parts within cooling department are new by now!