have a blown head gasket is my guess
If you do not have any external leaks, a head gasket is most likely.
Probably the thermostat is sticking.
i have replace the thermostat, checked the fans,filled with water and it is still overheating. Very often, the waterpump leaks and stops working only years after it was last replaced. Coolant is probably not flowing from the engine to the radiator to be cooled.
check thermostat, first, then look for radiator leaks, hoses that might be leaking.
A thermostat that is stuck in the closed position is a very common cause of overheating. A new thermostat should be installed every time the coolant is changed.
If your engine is overheating and has no obvious leaks then suspect the thermostat. Of course you can remove it and check it, but the best thing to do is just replace it if it is suspect. It should be replaced every time you service the cooling system. when you turn your heater on the it wont blow hot air
check thermostat. check engine fan coolant sensor possible locations radiator or thermostat housing. check electric fan working
The radiator may be plugged. Take it to a radiator shop.
Ingeneral, the fan will run only if the temperature of the radiator is above the normal range. If the fan is running, then the radiator must be over temp unless the radiator fan thermostat or it's relay is defective. If the radiator truly is over temp then you have a larger over-heating problem You state the thermostat was replaced. if you replaced the fan thermostat then either the radiator really is over temp and it is doing what it should, or there is a problem with the thermostat-fan relay or switch. If you replaced the engine thermostat that controls the flow of coolent between the engine and the radiator, then that probably wasn't your problem and you should look elsewhere for an overheating cause. I would start by determining if the engine actually is overheating or not. If it is, I would look for coolent system problems like the engine thermostat (if you didn't replace it already), water pump, leaks, scale build up in the radiator, or blockages in the system. If the engine isn't overheating then I would consentrate on the fan, fan thermostat and relays.
A couple possibilities are: low coolant level or bad water pump. just based on overheating and no heat, sounds like the thermostat is bad or it could be the water pump thermostat
It could just be that the water pump is not properly working. Have you checked all the could-be causes for your car overheating if not then do so.
bad fan clutch, could lead to stuck thermostat, just had both replaced on my 2000 w/ no visible leaks, 5.3 1500, 170K miles $200.00 service