bmw 318ti? 1996 4cyl?

overheating , I changed the water pump ,I haved changed the thermostat, made sure that there was no air in the radadior and antifreeze was full. I didn't have any heat and the fan came on once, but I haven't heard it come on like I think it should. It maybe the fan but I don't know how to check It. I am try of trying to figuring out what it is.Help some one!!!!!!!