If this only happened after changing the thermostat and radiator then firstly check there is not an airlock in the system! Then check the thermostat is the correct one for your vehicle and not faulty!
Could be one of the oil coolers, transmission or motor oil. also if it has electric fan there will be a temperature sending unit that tells the fan when to come on.
Answers & Comments
If this only happened after changing the thermostat and radiator then firstly check there is not an airlock in the system!
Then check the thermostat is the correct one for your vehicle and not faulty!
Could be one of the oil coolers, transmission or motor oil. also if it has electric fan there will be a temperature sending unit that tells the fan when to come on.