Try replacing the radiator fuse relay
When the thermostat and radiator were replaced, coolant could have dripped into an electrical connector or a sensor could be disconnected or damaged. Check the temperature sensor and crankshaft sensors first.
You need to check coolant temperature sensor and the water pump.
Blown head gastet, radiator leaking, thermostat needs to be replaced Blown head gastet, radiator leaking, thermostat needs to be replaced
Be careful there is a temperature coolant switch mounted next to the thermostat housing. I thought this was the sensor and replaced it by mistake. There is another sensor.
The thermostat on a 2004 Chevy Venture is changed by draining the radiator, removing the upper radiator hose, and unbolting the thermostat housing. The old thermostat and gasket can then be removed and replaced.
the hoses leading to and from your radiator might be clogged. If you had a rusty radiator, the rust may have clogged the hoses that carry the coolant. you should check all your hoses and even flush them out.
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.
The lower radiator hose goes from the bottom of the radiator to the engine block. On the engine side there will be a neck that comes off the block and the radiator hose is attached too it. Inside that neck is the thermostat and it can be replaced as a whole unit (the housing neck) or just the thermostat can be removed and replaced.
If the engine is taking a long time to warm up or the gauge registers low heat the thermostat probably is stuck open and needs to be replaced. If the engine runs hot check the temperature of the upper radiator hose. If it's not hot the thermostat is stuck closed and should be replaced. If the upper hose is hot it means the thermostat is open and working. Cooling problem could be restricted radiator.
The thermostat or the fan relay for the radiator fan. If the temperature gauge shows the engine to be hot the fan should be on. If the fan isn't on you can check it by removing the electrical connection to the temperature sensor. If the fan is all right it will come on by default when the wiring connector is removed. Usually it is the thermostat which needs to be replaced when the engine is overheating. If the top hose going to the radiator isn't hot when the temperature gauge shows the engine to be hot the thermostat is stuck shut and should be replaced.
The thermostat on a Nissan X-Trail is replaced by draining the radiator, disconnecting the upper radiator hose, removing the thermostat housing, and pulling out the thermostat. A new thermostat can be dropped into place and a new gasket installed.
The best indication of a bad thermostat is when the radiator fluid (Antifreeze) boils over from the reserve tank, not the radiator. This is caused by the thermostat not opening at its preset temperature and all the extra antifreeze is pumped directly to the reserve tank. You will also have loss of power and the vehicle will likely stop running soon after the antifreeze boils over.