if your fans are turning on then it is not the fan and you do not need to replace them... if they are not turning on then you have a problem with either the fan or the fan switch...

also, it could be the thermostate...

if non of the above... then it is either a cracked radiator (if fluid is low)... if not then it could be your water pump...

this is an easy system and there are only a few parts to them... look it over a little better and get back to us...
-Keith